Var: separating nxt_tstr_t from nxt_var_t.

It's for the introduction of njs support.
For each option that supports native variable and JS template literals introduced next,
it's unified as template string.

No functional changes.

17 files changed, 403 insertions, 226 deletions

diff --git a/auto/sources b/auto/sources
index 8f07cc0c..7d3f62cf 100644
--- a/auto/sources
+++ b/auto/sources
@@ -34,6 +34,7 @@ NXT_LIB_SRCS=" \
     src/nxt_parse.c \
     src/nxt_sprintf.c \
     src/nxt_var.c \
+    src/nxt_tstr.c \
     src/nxt_file_name.c \
     src/nxt_log.c \
     src/nxt_djb_hash.c \
diff --git a/src/nxt_conf.h b/src/nxt_conf.h
index c8a276c0..1b13f5ae 100644
--- a/src/nxt_conf.h
+++ b/src/nxt_conf.h
@@ -72,7 +72,7 @@ typedef struct {
     nxt_mp_t             *pool;
     nxt_str_t            error;
     void                 *ctx;
-    nxt_array_t          *var_fields;  /* of nxt_var_field_t */
+    nxt_tstr_state_t     *tstr_state;
     nxt_mp_t             *conf_pool;
     nxt_uint_t           ver;
 } nxt_conf_validation_t;
diff --git a/src/nxt_conf_validation.c b/src/nxt_conf_validation.c
index 7fbe7e29..09b3be55 100644
--- a/src/nxt_conf_validation.c
+++ b/src/nxt_conf_validation.c
@@ -1227,8 +1227,8 @@ nxt_conf_validate(nxt_conf_validation_t *vldt)
 {
     nxt_int_t  ret;
 
-    vldt->var_fields = nxt_array_create(vldt->pool, 4, sizeof(nxt_var_field_t));
-    if (nxt_slow_path(vldt->var_fields == NULL)) {
+    vldt->tstr_state = nxt_tstr_state_new(vldt->pool);
+    if (nxt_slow_path(vldt->tstr_state == NULL)) {
         return NXT_ERROR;
     }
 
@@ -1364,7 +1364,7 @@ nxt_conf_vldt_var(nxt_conf_validation_t *vldt, nxt_str_t *name,
 {
     u_char  error[NXT_MAX_ERROR_STR];
 
-    if (nxt_var_test(value, vldt->var_fields, error) != NXT_OK) {
+    if (nxt_tstr_test(vldt->tstr_state, value, error) != NXT_OK) {
         return nxt_conf_vldt_error(vldt, "%s in the \"%V\" value.",
                                    error, name);
     }
diff --git a/src/nxt_http.h b/src/nxt_http.h
index d5bff712..e29fe60a 100644
--- a/src/nxt_http.h
+++ b/src/nxt_http.h
@@ -169,7 +169,8 @@ struct nxt_http_request_s {
     nxt_timer_t                     timer;
     void                            *timer_data;
 
-    nxt_var_query_t                 *var_query;
+    nxt_tstr_query_t                *tstr_query;
+    nxt_var_cache_t                 var_cache;
 
     void                            *req_rpc_data;
 
@@ -245,7 +246,7 @@ struct nxt_http_action_s {
         nxt_http_route_t            *route;
         nxt_upstream_t              *upstream;
         uint32_t                    upstream_number;
-        nxt_var_t                   *var;
+        nxt_tstr_t                  *tstr;
         nxt_str_t                   *pass;
     } u;
 
diff --git a/src/nxt_http_request.c b/src/nxt_http_request.c
index 5c1455bf..84a67415 100644
--- a/src/nxt_http_request.c
+++ b/src/nxt_http_request.c
@@ -282,6 +282,8 @@ nxt_http_request_create(nxt_task_t *task)
 
     task->thread->engine->requests_cnt++;
 
+    r->var_cache.pool = mp;
+
     return r;
 
 fail:
@@ -795,7 +797,7 @@ nxt_http_request_error_handler(nxt_task_t *task, void *obj, void *data)
 void
 nxt_http_request_close_handler(nxt_task_t *task, void *obj, void *data)
 {
-    nxt_var_t                *log_format;
+    nxt_tstr_t               *log_format;
     nxt_http_proto_t         proto;
     nxt_http_request_t       *r;
     nxt_http_protocol_t      protocol;
diff --git a/src/nxt_http_return.c b/src/nxt_http_return.c
index 9f3c4fc5..63c7e06f 100644
--- a/src/nxt_http_return.c
+++ b/src/nxt_http_return.c
@@ -9,7 +9,7 @@
 
 typedef struct {
     nxt_http_status_t  status;
-    nxt_var_t          *location;
+    nxt_tstr_t         *location;
     nxt_str_t          encoded;
 } nxt_http_return_conf_t;
 
@@ -25,7 +25,7 @@ static nxt_http_action_t *nxt_http_return(nxt_task_t *task,
 static nxt_int_t nxt_http_return_encode(nxt_mp_t *mp, nxt_str_t *encoded,
     const nxt_str_t *location);
 static void nxt_http_return_send_ready(nxt_task_t *task, void *obj, void *data);
-static void nxt_http_return_var_error(nxt_task_t *task, void *obj, void *data);
+static void nxt_http_return_send_error(nxt_task_t *task, void *obj, void *data);
 
 
 static const nxt_http_request_state_t  nxt_http_return_send_state;
@@ -57,13 +57,13 @@ nxt_http_return_init(nxt_router_conf_t *rtcf, nxt_http_action_t *action,
 
     nxt_conf_get_string(acf->location, &str);
 
-    conf->location = nxt_var_compile(&str, mp, rtcf->var_fields, 0);
+    conf->location = nxt_tstr_compile(rtcf->tstr_state, &str, 0);
     if (nxt_slow_path(conf->location == NULL)) {
         return NXT_ERROR;
     }
 
-    if (nxt_var_is_const(conf->location)) {
-        nxt_var_raw(conf->location, &str);
+    if (nxt_tstr_is_const(conf->location)) {
+        nxt_tstr_str(conf->location, &str);
         return nxt_http_return_encode(mp, &conf->encoded, &str);
     }
 
@@ -76,6 +76,7 @@ nxt_http_return(nxt_task_t *task, nxt_http_request_t *r,
     nxt_http_action_t *action)
 {
     nxt_int_t               ret;
+    nxt_router_conf_t       *rtcf;
     nxt_http_return_ctx_t   *ctx;
     nxt_http_return_conf_t  *conf;
 
@@ -88,7 +89,7 @@ nxt_http_return(nxt_task_t *task, nxt_http_request_t *r,
         nxt_str_set(&loc, "");
 
     } else {
-        nxt_var_raw(conf->location, &loc);
+        nxt_tstr_str(conf->location, &loc);
     }
 
     nxt_debug(task, "http return: %d (loc: \"%V\")", conf->status, &loc);
@@ -114,7 +115,7 @@ nxt_http_return(nxt_task_t *task, nxt_http_request_t *r,
     r->status = conf->status;
     r->resp.content_length_n = 0;
 
-    if (ctx == NULL || nxt_var_is_const(conf->location)) {
+    if (ctx == NULL || nxt_tstr_is_const(conf->location)) {
         if (ctx != NULL) {
             ctx->encoded = conf->encoded;
         }
@@ -122,16 +123,19 @@ nxt_http_return(nxt_task_t *task, nxt_http_request_t *r,
         nxt_http_return_send_ready(task, r, ctx);
 
     } else {
-        ret = nxt_var_query_init(&r->var_query, r, r->mem_pool);
+        rtcf = r->conf->socket_conf->router_conf;
+
+        ret = nxt_tstr_query_init(&r->tstr_query, rtcf->tstr_state,
+                                  &r->var_cache, r, r->mem_pool);
         if (nxt_slow_path(ret != NXT_OK)) {
             goto fail;
         }
 
-        nxt_var_query(task, r->var_query, conf->location, &ctx->location);
+        nxt_tstr_query(task, r->tstr_query, conf->location, &ctx->location);
 
-        nxt_var_query_resolve(task, r->var_query, ctx,
-                              nxt_http_return_send_ready,
-                              nxt_http_return_var_error);
+        nxt_tstr_query_resolve(task, r->tstr_query, ctx,
+                               nxt_http_return_send_ready,
+                               nxt_http_return_send_error);
     }
 
     return NULL;
@@ -213,7 +217,7 @@ fail:
 
 
 static void
-nxt_http_return_var_error(nxt_task_t *task, void *obj, void *data)
+nxt_http_return_send_error(nxt_task_t *task, void *obj, void *data)
 {
     nxt_http_request_t  *r;
 
diff --git a/src/nxt_http_route.c b/src/nxt_http_route.c
index 1f2fe883..77a59e9c 100644
--- a/src/nxt_http_route.c
+++ b/src/nxt_http_route.c
@@ -193,8 +193,8 @@ static nxt_int_t nxt_http_action_resolve(nxt_task_t *task,
     nxt_router_temp_conf_t *tmcf, nxt_http_action_t *action);
 static nxt_http_action_t *nxt_http_pass_var(nxt_task_t *task,
     nxt_http_request_t *r, nxt_http_action_t *action);
-static void nxt_http_pass_var_ready(nxt_task_t *task, void *obj, void *data);
-static void nxt_http_pass_var_error(nxt_task_t *task, void *obj, void *data);
+static void nxt_http_pass_query_ready(nxt_task_t *task, void *obj, void *data);
+static void nxt_http_pass_query_error(nxt_task_t *task, void *obj, void *data);
 static nxt_int_t nxt_http_pass_find(nxt_mp_t *mp, nxt_router_conf_t *rtcf,
     nxt_str_t *pass, nxt_http_action_t *action);
 static nxt_int_t nxt_http_route_find(nxt_http_routes_t *routes, nxt_str_t *name,
@@ -673,8 +673,8 @@ nxt_http_action_init(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
 
     nxt_conf_get_string(acf.pass, &pass);
 
-    action->u.var = nxt_var_compile(&pass, mp, rtcf->var_fields, 0);
-    if (nxt_slow_path(action->u.var == NULL)) {
+    action->u.tstr = nxt_tstr_compile(rtcf->tstr_state, &pass, 0);
+    if (nxt_slow_path(action->u.tstr == NULL)) {
         return NXT_ERROR;
     }
 
@@ -1272,8 +1272,8 @@ nxt_http_action_resolve(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
         return NXT_OK;
     }
 
-    if (nxt_var_is_const(action->u.var)) {
-        nxt_var_raw(action->u.var, &pass);
+    if (nxt_tstr_is_const(action->u.tstr)) {
+        nxt_tstr_str(action->u.tstr, &pass);
 
         ret = nxt_http_pass_find(tmcf->mem_pool, tmcf->router_conf, &pass,
                                  action);
@@ -1293,17 +1293,21 @@ static nxt_http_action_t *
 nxt_http_pass_var(nxt_task_t *task, nxt_http_request_t *r,
     nxt_http_action_t *action)
 {
-    nxt_int_t  ret;
-    nxt_str_t  str;
-    nxt_var_t  *var;
+    nxt_int_t          ret;
+    nxt_str_t          str;
+    nxt_tstr_t         *tstr;
+    nxt_router_conf_t  *rtcf;
 
-    var = action->u.var;
+    tstr = action->u.tstr;
 
-    nxt_var_raw(var, &str);
+    nxt_tstr_str(tstr, &str);
 
     nxt_debug(task, "http pass: \"%V\"", &str);
 
-    ret = nxt_var_query_init(&r->var_query, r, r->mem_pool);
+    rtcf = r->conf->socket_conf->router_conf;
+
+    ret = nxt_tstr_query_init(&r->tstr_query, rtcf->tstr_state, &r->var_cache,
+                              r, r->mem_pool);
     if (nxt_slow_path(ret != NXT_OK)) {
         goto fail;
     }
@@ -1316,10 +1320,10 @@ nxt_http_pass_var(nxt_task_t *task, nxt_http_request_t *r,
 
     action->u.pass = nxt_pointer_to(action, sizeof(nxt_http_action_t));
 
-    nxt_var_query(task, r->var_query, var, action->u.pass);
-    nxt_var_query_resolve(task, r->var_query, action,
-                          nxt_http_pass_var_ready,
-                          nxt_http_pass_var_error);
+    nxt_tstr_query(task, r->tstr_query, tstr, action->u.pass);
+    nxt_tstr_query_resolve(task, r->tstr_query, action,
+                           nxt_http_pass_query_ready,
+                           nxt_http_pass_query_error);
     return NULL;
 
 fail:
@@ -1330,7 +1334,7 @@ fail:
 
 
 static void
-nxt_http_pass_var_ready(nxt_task_t *task, void *obj, void *data)
+nxt_http_pass_query_ready(nxt_task_t *task, void *obj, void *data)
 {
     nxt_int_t           ret;
     nxt_router_conf_t   *rtcf;
@@ -1359,7 +1363,7 @@ nxt_http_pass_var_ready(nxt_task_t *task, void *obj, void *data)
 
 
 static void
-nxt_http_pass_var_error(nxt_task_t *task, void *obj, void *data)
+nxt_http_pass_query_error(nxt_task_t *task, void *obj, void *data)
 {
     nxt_http_request_t  *r;
 
@@ -1497,8 +1501,8 @@ nxt_http_action_create(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
         return NULL;
     }
 
-    action->u.var = nxt_var_compile(pass, mp, rtcf->var_fields, 0);
-    if (nxt_slow_path(action->u.var == NULL)) {
+    action->u.tstr = nxt_tstr_compile(rtcf->tstr_state, pass, 0);
+    if (nxt_slow_path(action->u.tstr == NULL)) {
         return NULL;
     }
 
diff --git a/src/nxt_http_static.c b/src/nxt_http_static.c
index 0507e038..7143ecd3 100644
--- a/src/nxt_http_static.c
+++ b/src/nxt_http_static.c
@@ -8,7 +8,7 @@
 
 
 typedef struct {
-    nxt_var_t                   *var;
+    nxt_tstr_t                  *tstr;
 #if (NXT_HAVE_OPENAT2)
     u_char                      *fname;
 #endif
@@ -21,7 +21,7 @@ typedef struct {
     nxt_http_static_share_t     *shares;
     nxt_str_t                   index;
 #if (NXT_HAVE_OPENAT2)
-    nxt_var_t                   *chroot;
+    nxt_tstr_t                  *chroot;
     nxt_uint_t                  resolve;
 #endif
     nxt_http_route_rule_t       *types;
@@ -48,7 +48,7 @@ static nxt_http_action_t *nxt_http_static(nxt_task_t *task,
 static void nxt_http_static_iterate(nxt_task_t *task, nxt_http_request_t *r,
     nxt_http_static_ctx_t *ctx);
 static void nxt_http_static_send_ready(nxt_task_t *task, void *obj, void *data);
-static void nxt_http_static_var_error(nxt_task_t *task, void *obj, void *data);
+static void nxt_http_static_send_error(nxt_task_t *task, void *obj, void *data);
 static void nxt_http_static_next(nxt_task_t *task, nxt_http_request_t *r,
     nxt_http_static_ctx_t *ctx, nxt_http_status_t status);
 #if (NXT_HAVE_OPENAT2)
@@ -77,7 +77,7 @@ nxt_http_static_init(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
     uint32_t                i;
     nxt_mp_t                *mp;
     nxt_str_t               str, *ret;
-    nxt_var_t               *var;
+    nxt_tstr_t              *tstr;
     nxt_conf_value_t        *cv;
     nxt_router_conf_t       *rtcf;
     nxt_http_static_conf_t  *conf;
@@ -104,13 +104,13 @@ nxt_http_static_init(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
         cv = nxt_conf_get_array_element_or_itself(acf->share, i);
         nxt_conf_get_string(cv, &str);
 
-        var = nxt_var_compile(&str, mp, rtcf->var_fields, NXT_VAR_STRZ);
-        if (nxt_slow_path(var == NULL)) {
+        tstr = nxt_tstr_compile(rtcf->tstr_state, &str, NXT_TSTR_STRZ);
+        if (nxt_slow_path(tstr == NULL)) {
             return NXT_ERROR;
         }
 
-        conf->shares[i].var = var;
-        conf->shares[i].is_const = nxt_var_is_const(var);
+        conf->shares[i].tstr = tstr;
+        conf->shares[i].is_const = nxt_tstr_is_const(tstr);
     }
 
     if (acf->index == NULL) {
@@ -130,20 +130,20 @@ nxt_http_static_init(nxt_task_t *task, nxt_router_temp_conf_t *tmcf,
         nxt_str_t   chr, shr;
         nxt_bool_t  is_const;
 
-        conf->chroot = nxt_var_compile(&acf->chroot, mp, rtcf->var_fields,
-                                       NXT_VAR_STRZ);
+        conf->chroot = nxt_tstr_compile(rtcf->tstr_state, &acf->chroot,
+                                        NXT_TSTR_STRZ);
         if (nxt_slow_path(conf->chroot == NULL)) {
             return NXT_ERROR;
         }
 
-        is_const = nxt_var_is_const(conf->chroot);
+        is_const = nxt_tstr_is_const(conf->chroot);
 
         for (i = 0; i < conf->nshares; i++) {
             conf->shares[i].is_const &= is_const;
 
             if (conf->shares[i].is_const) {
-                nxt_var_raw(conf->chroot, &chr);
-                nxt_var_raw(conf->shares[i].var, &shr);
+                nxt_tstr_str(conf->chroot, &chr);
+                nxt_tstr_str(conf->shares[i].tstr, &shr);
 
                 conf->shares[i].fname = nxt_http_static_chroot_match(chr.start,
                                                                      shr.start);
@@ -229,6 +229,7 @@ nxt_http_static_iterate(nxt_task_t *task, nxt_http_request_t *r,
     nxt_http_static_ctx_t *ctx)
 {
     nxt_int_t                ret;
+    nxt_router_conf_t        *rtcf;
     nxt_http_static_conf_t   *conf;
     nxt_http_static_share_t  *share;
 
@@ -240,14 +241,14 @@ nxt_http_static_iterate(nxt_task_t *task, nxt_http_request_t *r,
     nxt_str_t  shr;
     nxt_str_t  idx;
 
-    nxt_var_raw(share->var, &shr);
+    nxt_tstr_str(share->tstr, &shr);
     idx = conf->index;
 
 #if (NXT_HAVE_OPENAT2)
     nxt_str_t  chr;
 
     if (conf->chroot != NULL) {
-        nxt_var_raw(conf->chroot, &chr);
+        nxt_tstr_str(conf->chroot, &chr);
 
     } else {
         nxt_str_set(&chr, "");
@@ -261,34 +262,37 @@ nxt_http_static_iterate(nxt_task_t *task, nxt_http_request_t *r,
 #endif /* NXT_DEBUG */
 
     if (share->is_const) {
-        nxt_var_raw(share->var, &ctx->share);
+        nxt_tstr_str(share->tstr, &ctx->share);
 
 #if (NXT_HAVE_OPENAT2)
         if (conf->chroot != NULL && ctx->share_idx == 0) {
-            nxt_var_raw(conf->chroot, &ctx->chroot);
+            nxt_tstr_str(conf->chroot, &ctx->chroot);
         }
 #endif
 
         nxt_http_static_send_ready(task, r, ctx);
 
     } else {
-        ret = nxt_var_query_init(&r->var_query, r, r->mem_pool);
+        rtcf = r->conf->socket_conf->router_conf;
+
+        ret = nxt_tstr_query_init(&r->tstr_query, rtcf->tstr_state,
+                                  &r->var_cache, r, r->mem_pool);
         if (nxt_slow_path(ret != NXT_OK)) {
             nxt_http_request_error(task, r, NXT_HTTP_INTERNAL_SERVER_ERROR);
             return;
         }
 
-        nxt_var_query(task, r->var_query, share->var, &ctx->share);
+        nxt_tstr_query(task, r->tstr_query, share->tstr, &ctx->share);
 
 #if (NXT_HAVE_OPENAT2)
         if (conf->chroot != NULL && ctx->share_idx == 0) {
-            nxt_var_query(task, r->var_query, conf->chroot, &ctx->chroot);
+            nxt_tstr_query(task, r->tstr_query, conf->chroot, &ctx->chroot);
         }
 #endif
 
-        nxt_var_query_resolve(task, r->var_query, ctx,
-                              nxt_http_static_send_ready,
-                              nxt_http_static_var_error);
+        nxt_tstr_query_resolve(task, r->tstr_query, ctx,
+                               nxt_http_static_send_ready,
+                               nxt_http_static_send_error);
      }
 }
 
@@ -658,7 +662,7 @@ fail:
 
 
 static void
-nxt_http_static_var_error(nxt_task_t *task, void *obj, void *data)
+nxt_http_static_send_error(nxt_task_t *task, void *obj, void *data)
 {
     nxt_http_request_t  *r;
 
diff --git a/src/nxt_http_variables.c b/src/nxt_http_variables.c
index eb341716..fa0244db 100644
--- a/src/nxt_http_variables.c
+++ b/src/nxt_http_variables.c
@@ -407,7 +407,7 @@ nxt_http_var_arg(nxt_task_t *task, nxt_str_t *str, void *ctx, uint16_t field)
 
     rtcf = r->conf->socket_conf->router_conf;
 
-    vf = nxt_var_field_get(rtcf->var_fields, field);
+    vf = nxt_var_field_get(rtcf->tstr_state->var_fields, field);
 
     args = nxt_http_arguments_parse(r);
     if (nxt_slow_path(args == NULL)) {
@@ -450,7 +450,7 @@ nxt_http_var_header(nxt_task_t *task, nxt_str_t *str, void *ctx, uint16_t field)
 
     rtcf = r->conf->socket_conf->router_conf;
 
-    vf = nxt_var_field_get(rtcf->var_fields, field);
+    vf = nxt_var_field_get(rtcf->tstr_state->var_fields, field);
 
     nxt_list_each(f, r->fields) {
 
@@ -485,7 +485,7 @@ nxt_http_var_cookie(nxt_task_t *task, nxt_str_t *str, void *ctx, uint16_t field)
 
     rtcf = r->conf->socket_conf->router_conf;
 
-    vf = nxt_var_field_get(rtcf->var_fields, field);
+    vf = nxt_var_field_get(rtcf->tstr_state->var_fields, field);
 
     cookies = nxt_http_cookies_parse(r);
     if (nxt_slow_path(cookies == NULL)) {
diff --git a/src/nxt_main.h b/src/nxt_main.h
index a51a1ce7..b0cdc2d3 100644
--- a/src/nxt_main.h
+++ b/src/nxt_main.h
@@ -68,6 +68,7 @@ typedef uint16_t                     nxt_port_id_t;
 #include <nxt_sprintf.h>
 #include <nxt_parse.h>
 #include <nxt_var.h>
+#include <nxt_tstr.h>
 
 
 /* TODO: remove unused */
diff --git a/src/nxt_router.c b/src/nxt_router.c
index cfd79bf5..3ad78fa4 100644
--- a/src/nxt_router.c
+++ b/src/nxt_router.c
@@ -1060,8 +1060,8 @@ nxt_router_temp_conf(nxt_task_t *task)
 
     rtcf->mem_pool = mp;
 
-    rtcf->var_fields = nxt_array_create(mp, 4, sizeof(nxt_var_field_t));
-    if (nxt_slow_path(rtcf->var_fields == NULL)) {
+    rtcf->tstr_state = nxt_tstr_state_new(mp);
+    if (nxt_slow_path(rtcf->tstr_state == NULL)) {
         goto fail;
     }
 
diff --git a/src/nxt_router.h b/src/nxt_router.h
index a6add219..11094960 100644
--- a/src/nxt_router.h
+++ b/src/nxt_router.h
@@ -43,7 +43,7 @@ typedef struct {
     uint32_t                 threads;
 
     nxt_mp_t                 *mem_pool;
-    nxt_array_t              *var_fields;  /* of nxt_var_field_t */
+    nxt_tstr_state_t         *tstr_state;
 
     nxt_router_t             *router;
     nxt_http_routes_t        *routes;
@@ -53,7 +53,7 @@ typedef struct {
     nxt_lvlhsh_t             apps_hash;
 
     nxt_router_access_log_t  *access_log;
-    nxt_var_t                *log_format;
+    nxt_tstr_t               *log_format;
 } nxt_router_conf_t;
 
 
@@ -225,7 +225,7 @@ typedef struct {
 struct nxt_router_access_log_s {
     void                   (*handler)(nxt_task_t *task, nxt_http_request_t *r,
                                       nxt_router_access_log_t *access_log,
-                                      nxt_var_t *format);
+                                      nxt_tstr_t *format);
     nxt_fd_t               fd;
     nxt_str_t              path;
     uint32_t               count;
diff --git a/src/nxt_router_access_log.c b/src/nxt_router_access_log.c
index dc2a6687..9da366f4 100644
--- a/src/nxt_router_access_log.c
+++ b/src/nxt_router_access_log.c
@@ -24,7 +24,7 @@ typedef struct {
 
 static void nxt_router_access_log_writer(nxt_task_t *task,
     nxt_http_request_t *r, nxt_router_access_log_t *access_log,
-    nxt_var_t *format);
+    nxt_tstr_t *format);
 static void nxt_router_access_log_write_ready(nxt_task_t *task, void *obj,
     void *data);
 static void nxt_router_access_log_write_error(nxt_task_t *task, void *obj,
@@ -63,7 +63,7 @@ nxt_router_access_log_create(nxt_task_t *task, nxt_router_conf_t *rtcf,
     u_char                        *p;
     nxt_int_t                     ret;
     nxt_str_t                     str;
-    nxt_var_t                     *format;
+    nxt_tstr_t                    *format;
     nxt_router_t                  *router;
     nxt_router_access_log_t       *access_log;
     nxt_router_access_log_conf_t  alcf;
@@ -125,8 +125,7 @@ nxt_router_access_log_create(nxt_task_t *task, nxt_router_conf_t *rtcf,
     p = nxt_cpymem(str.start, alcf.format.start, alcf.format.length);
     *p = '\n';
 
-    format = nxt_var_compile(&str, rtcf->mem_pool, rtcf->var_fields,
-                             NXT_VAR_LOGGING);
+    format = nxt_tstr_compile(rtcf->tstr_state, &str, NXT_TSTR_LOGGING);
     if (nxt_slow_path(format == NULL)) {
         return NXT_ERROR;
     }
@@ -140,9 +139,10 @@ nxt_router_access_log_create(nxt_task_t *task, nxt_router_conf_t *rtcf,
 
 static void
 nxt_router_access_log_writer(nxt_task_t *task, nxt_http_request_t *r,
-    nxt_router_access_log_t *access_log, nxt_var_t *format)
+    nxt_router_access_log_t *access_log, nxt_tstr_t *format)
 {
     nxt_int_t                    ret;
+    nxt_router_conf_t            *rtcf;
     nxt_router_access_log_ctx_t  *ctx;
 
     ctx = nxt_mp_get(r->mem_pool, sizeof(nxt_router_access_log_ctx_t));
@@ -152,21 +152,24 @@ nxt_router_access_log_writer(nxt_task_t *task, nxt_http_request_t *r,
 
     ctx->access_log = access_log;
 
-    if (nxt_var_is_const(format)) {
-        nxt_var_raw(format, &ctx->text);
+    if (nxt_tstr_is_const(format)) {
+        nxt_tstr_str(format, &ctx->text);
 
         nxt_router_access_log_write_ready(task, r, ctx);
 
     } else {
-        ret = nxt_var_query_init(&r->var_query, r, r->mem_pool);
+        rtcf = r->conf->socket_conf->router_conf;
+
+        ret = nxt_tstr_query_init(&r->tstr_query, rtcf->tstr_state,
+                                  &r->var_cache, r, r->mem_pool);
         if (nxt_slow_path(ret != NXT_OK)) {
             return;
         }
 
-        nxt_var_query(task, r->var_query, format, &ctx->text);
-        nxt_var_query_resolve(task, r->var_query, ctx,
-                              nxt_router_access_log_write_ready,
-                              nxt_router_access_log_write_error);
+        nxt_tstr_query(task, r->tstr_query, format, &ctx->text);
+        nxt_tstr_query_resolve(task, r->tstr_query, ctx,
+                               nxt_router_access_log_write_ready,
+                               nxt_router_access_log_write_error);
      }
 }
 
diff --git a/src/nxt_tstr.c b/src/nxt_tstr.c
new file mode 100644
index 00000000..dff61952
--- /dev/null
+++ b/src/nxt_tstr.c
@@ -0,0 +1,223 @@
+
+/*
+ * Copyright (C) NGINX, Inc.
+ */
+
+#include <nxt_main.h>
+
+
+typedef enum {
+    NXT_TSTR_CONST = 0,
+    NXT_TSTR_VAR,
+} nxt_tstr_type_t;
+
+
+struct nxt_tstr_s {
+    nxt_str_t           str;
+    nxt_var_t           *var;
+    nxt_tstr_flags_t    flags;
+    nxt_tstr_type_t     type;
+};
+
+
+struct nxt_tstr_query_s {
+    nxt_mp_t            *pool;
+
+    nxt_tstr_state_t    *state;
+    nxt_var_cache_t     *cache;
+
+    nxt_uint_t          waiting;
+    nxt_uint_t          failed;   /* 1 bit */
+
+    void                *ctx;
+    void                *data;
+
+   nxt_work_handler_t  ready;
+   nxt_work_handler_t  error;
+};
+
+
+nxt_tstr_state_t *
+nxt_tstr_state_new(nxt_mp_t *mp)
+{
+    nxt_tstr_state_t  *state;
+
+    state = nxt_mp_get(mp, sizeof(nxt_tstr_state_t));
+    if (nxt_slow_path(state == NULL)) {
+        return NULL;
+    }
+
+    state->pool = mp;
+
+    state->var_fields = nxt_array_create(mp, 4, sizeof(nxt_var_field_t));
+    if (nxt_slow_path(state->var_fields == NULL)) {
+        return NULL;
+    }
+
+    return state;
+}
+
+
+nxt_tstr_t *
+nxt_tstr_compile(nxt_tstr_state_t *state, nxt_str_t *str,
+    nxt_tstr_flags_t flags)
+{
+    u_char      *p;
+    nxt_tstr_t  *tstr;
+    nxt_bool_t  strz;
+
+    strz = (flags & NXT_TSTR_STRZ) != 0;
+
+    tstr = nxt_mp_get(state->pool, sizeof(nxt_tstr_t));
+    if (nxt_slow_path(tstr == NULL)) {
+        return NULL;
+    }
+
+    tstr->str.length = str->length + strz;
+
+    tstr->str.start = nxt_mp_nget(state->pool, tstr->str.length);
+    if (nxt_slow_path(tstr->str.start == NULL)) {
+        return NULL;
+    }
+
+    p = nxt_cpymem(tstr->str.start, str->start, str->length);
+
+    if (strz) {
+        *p = '\0';
+    }
+
+    tstr->flags = flags;
+
+    p = nxt_memchr(str->start, '$', str->length);
+
+    if (p != NULL) {
+        tstr->type = NXT_TSTR_VAR;
+
+        tstr->var = nxt_var_compile(&tstr->str, state->pool, state->var_fields);
+        if (nxt_slow_path(tstr->var == NULL)) {
+            return NULL;
+        }
+
+    } else {
+        tstr->type = NXT_TSTR_CONST;
+    }
+
+    return tstr;
+}
+
+
+nxt_int_t
+nxt_tstr_test(nxt_tstr_state_t *state, nxt_str_t *str, u_char *error)
+{
+    return nxt_var_test(str, state->var_fields, error);
+}
+
+
+nxt_bool_t
+nxt_tstr_is_const(nxt_tstr_t *tstr)
+{
+    return (tstr->type == NXT_TSTR_CONST);
+}
+
+
+void
+nxt_tstr_str(nxt_tstr_t *tstr, nxt_str_t *str)
+{
+    *str = tstr->str;
+
+    if (tstr->flags & NXT_TSTR_STRZ) {
+        str->length--;
+    }
+}
+
+
+nxt_int_t
+nxt_tstr_query_init(nxt_tstr_query_t **query_p, nxt_tstr_state_t *state,
+    nxt_var_cache_t *cache, void *ctx, nxt_mp_t *mp)
+{
+    nxt_tstr_query_t  *query;
+
+    query = *query_p;
+
+    if (*query_p == NULL) {
+        query = nxt_mp_zget(mp, sizeof(nxt_tstr_query_t));
+        if (nxt_slow_path(query == NULL)) {
+            return NXT_ERROR;
+        }
+    }
+
+    query->pool = mp;
+    query->state = state;
+    query->cache = cache;
+    query->ctx = ctx;
+
+    *query_p = query;
+
+    return NXT_OK;
+}
+
+
+void
+nxt_tstr_query(nxt_task_t *task, nxt_tstr_query_t *query, nxt_tstr_t *tstr,
+    nxt_str_t *val)
+{
+    nxt_int_t  ret;
+
+    if (nxt_tstr_is_const(tstr)) {
+        nxt_tstr_str(tstr, val);
+        return;
+    }
+
+    if (nxt_slow_path(query->failed)) {
+        return;
+    }
+
+    ret = nxt_var_interpreter(task, query->cache, tstr->var, val, query->ctx,
+                              tstr->flags & NXT_TSTR_LOGGING);
+    if (nxt_slow_path(ret != NXT_OK)) {
+        query->failed = 1;
+        return;
+    }
+
+    if (tstr->flags & NXT_TSTR_STRZ) {
+        val->length--;
+    }
+
+#if (NXT_DEBUG)
+    nxt_str_t  str;
+
+    nxt_tstr_str(tstr, &str);
+
+    nxt_debug(task, "tstr: \"%V\" -> \"%V\"", &str, val);
+#endif
+}
+
+
+void
+nxt_tstr_query_resolve(nxt_task_t *task, nxt_tstr_query_t *query, void *data,
+    nxt_work_handler_t ready, nxt_work_handler_t error)
+{
+    query->data = data;
+    query->ready = ready;
+    query->error = error;
+
+    if (query->waiting == 0) {
+        nxt_work_queue_add(&task->thread->engine->fast_work_queue,
+                           query->failed ? query->error : query->ready,
+                           task, query->ctx, query->data);
+    }
+}
+
+
+void
+nxt_tstr_query_handle(nxt_task_t *task, nxt_tstr_query_t *query,
+    nxt_bool_t failed)
+{
+    query->failed |= failed;
+
+    if (--query->waiting == 0) {
+        nxt_work_queue_add(&task->thread->engine->fast_work_queue,
+                           query->failed ? query->error : query->ready,
+                           task, query->ctx, query->data);
+    }
+}
diff --git a/src/nxt_tstr.h b/src/nxt_tstr.h
new file mode 100644
index 00000000..692b9d28
--- /dev/null
+++ b/src/nxt_tstr.h
@@ -0,0 +1,45 @@
+
+/*
+ * Copyright (C) NGINX, Inc.
+ */
+
+#ifndef _NXT_TSTR_H_INCLUDED_
+#define _NXT_TSTR_H_INCLUDED_
+
+
+typedef struct nxt_tstr_s        nxt_tstr_t;
+typedef struct nxt_tstr_query_s  nxt_tstr_query_t;
+
+
+typedef struct {
+    nxt_mp_t            *pool;
+    nxt_array_t         *var_fields;
+} nxt_tstr_state_t;
+
+
+typedef enum {
+    NXT_TSTR_STRZ       = 1 << 0,
+    NXT_TSTR_LOGGING    = 1 << 1,
+} nxt_tstr_flags_t;
+
+
+nxt_tstr_state_t *nxt_tstr_state_new(nxt_mp_t *mp);
+nxt_tstr_t *nxt_tstr_compile(nxt_tstr_state_t *state, nxt_str_t *str,
+    nxt_tstr_flags_t flags);
+nxt_int_t nxt_tstr_test(nxt_tstr_state_t *state, nxt_str_t *str, u_char *error);
+
+nxt_bool_t nxt_tstr_is_const(nxt_tstr_t *tstr);
+void nxt_tstr_str(nxt_tstr_t *tstr, nxt_str_t *str);
+
+nxt_int_t nxt_tstr_query_init(nxt_tstr_query_t **query_p,
+    nxt_tstr_state_t *state, nxt_var_cache_t *cache, void *ctx,
+    nxt_mp_t *mp);
+void nxt_tstr_query(nxt_task_t *task, nxt_tstr_query_t *query, nxt_tstr_t *tstr,
+    nxt_str_t *val);
+void nxt_tstr_query_resolve(nxt_task_t *task, nxt_tstr_query_t *query,
+    void *data, nxt_work_handler_t ready, nxt_work_handler_t error);
+void nxt_tstr_query_handle(nxt_task_t *task, nxt_tstr_query_t *query,
+    nxt_bool_t failed);
+
+
+#endif /* _NXT_TSTR_H_INCLUDED_ */
diff --git a/src/nxt_var.c b/src/nxt_var.c
index c4133544..e113969f 100644
--- a/src/nxt_var.c
+++ b/src/nxt_var.c
@@ -9,7 +9,6 @@
 struct nxt_var_s {
     size_t              length;
     nxt_uint_t          vars;
-    nxt_var_flags_t     flags;
     u_char              data[];
 
 /*
@@ -29,8 +28,7 @@ typedef struct {
 struct nxt_var_query_s {
     nxt_mp_t            *pool;
 
-    nxt_lvlhsh_t        cache;
-    nxt_str_t           *spare;
+    nxt_var_cache_t     cache;
 
     nxt_uint_t          waiting;
     nxt_uint_t          failed;   /* 1 bit */
@@ -58,8 +56,8 @@ static nxt_var_field_t *nxt_var_field_add(nxt_array_t *fields, nxt_str_t *name,
     uint32_t hash);
 
 static nxt_int_t nxt_var_cache_test(nxt_lvlhsh_query_t *lhq, void *data);
-static nxt_str_t *nxt_var_cache_value(nxt_task_t *task, nxt_var_query_t *query,
-    uint32_t index);
+static nxt_str_t *nxt_var_cache_value(nxt_task_t *task, nxt_var_cache_t *cache,
+    uint32_t index, void *ctx);
 
 static u_char *nxt_var_next_part(u_char *start, u_char *end, nxt_str_t *part);
 
@@ -232,21 +230,22 @@ nxt_var_cache_test(nxt_lvlhsh_query_t *lhq, void *data)
 
 
 static nxt_str_t *
-nxt_var_cache_value(nxt_task_t *task, nxt_var_query_t *query, uint32_t index)
+nxt_var_cache_value(nxt_task_t *task, nxt_var_cache_t *cache, uint32_t index,
+    void *ctx)
 {
     nxt_int_t           ret;
     nxt_str_t           *value;
     nxt_lvlhsh_query_t  lhq;
 
-    value = query->spare;
+    value = cache->spare;
 
     if (value == NULL) {
-        value = nxt_mp_zget(query->pool, sizeof(nxt_str_t));
+        value = nxt_mp_zget(cache->pool, sizeof(nxt_str_t));
         if (nxt_slow_path(value == NULL)) {
             return NULL;
         }
 
-        query->spare = value;
+        cache->spare = value;
     }
 
     lhq.key_hash = nxt_murmur_hash2_uint32(&index);
@@ -255,21 +254,20 @@ nxt_var_cache_value(nxt_task_t *task, nxt_var_query_t *query, uint32_t index)
     lhq.key.start = (u_char *) &index;
     lhq.value = value;
     lhq.proto = &nxt_var_cache_proto;
-    lhq.pool = query->pool;
+    lhq.pool = cache->pool;
 
-    ret = nxt_lvlhsh_insert(&query->cache, &lhq);
+    ret = nxt_lvlhsh_insert(&cache->hash, &lhq);
     if (nxt_slow_path(ret == NXT_ERROR)) {
         return NULL;
     }
 
     if (ret == NXT_OK) {
-        ret = nxt_var_index[index >> 16](task, value, query->ctx,
-                                         index & 0xffff);
+        ret = nxt_var_index[index >> 16](task, value, ctx, index & 0xffff);
         if (nxt_slow_path(ret != NXT_OK)) {
             return NULL;
         }
 
-        query->spare = NULL;
+        cache->spare = NULL;
     }
 
     return lhq.value;
@@ -329,21 +327,17 @@ nxt_var_index_init(void)
 
 
 nxt_var_t *
-nxt_var_compile(nxt_str_t *str, nxt_mp_t *mp, nxt_array_t *fields,
-    nxt_var_flags_t flags)
+nxt_var_compile(nxt_str_t *str, nxt_mp_t *mp, nxt_array_t *fields)
 {
     u_char          *p, *end, *next, *src;
     size_t          size;
     uint32_t        index;
-    nxt_bool_t      strz;
     nxt_var_t       *var;
     nxt_str_t       part;
     nxt_uint_t      n;
     nxt_var_sub_t   *subs;
     nxt_var_decl_t  *decl;
 
-    strz = (flags & NXT_VAR_STRZ) != 0;
-
     n = 0;
 
     p = str->start;
@@ -362,24 +356,19 @@ nxt_var_compile(nxt_str_t *str, nxt_mp_t *mp, nxt_array_t *fields,
 
     size = sizeof(nxt_var_t) + n * sizeof(nxt_var_sub_t) + str->length;
 
-    var = nxt_mp_get(mp, size + strz);
+    var = nxt_mp_get(mp, size);
     if (nxt_slow_path(var == NULL)) {
         return NULL;
     }
 
     var->length = str->length;
     var->vars = n;
-    var->flags = flags;
 
     subs = nxt_var_subs(var);
     src = nxt_var_raw_start(var);
 
     nxt_memcpy(src, str->start, str->length);
 
-    if (strz) {
-        src[str->length] = '\0';
-    }
-
     n = 0;
     p = str->start;
 
@@ -514,84 +503,33 @@ nxt_var_next_part(u_char *start, u_char *end, nxt_str_t *part)
 }
 
 
-inline void
-nxt_var_raw(nxt_var_t *var, nxt_str_t *str)
-{
-    str->length = var->length;
-    str->start = nxt_var_raw_start(var);
-}
-
-
-inline nxt_bool_t
-nxt_var_is_const(nxt_var_t *var)
-{
-    return (var->vars == 0);
-}
-
-
 nxt_int_t
-nxt_var_query_init(nxt_var_query_t **query_p, void *ctx, nxt_mp_t *mp)
-{
-    nxt_var_query_t  *query;
-
-    query = *query_p;
-
-    if (*query_p == NULL) {
-        query = nxt_mp_zget(mp, sizeof(nxt_var_query_t));
-        if (nxt_slow_path(query == NULL)) {
-            return NXT_ERROR;
-        }
-    }
-
-    query->pool = mp;
-    query->ctx = ctx;
-
-    *query_p = query;
-
-    return NXT_OK;
-}
-
-
-void
-nxt_var_query(nxt_task_t *task, nxt_var_query_t *query, nxt_var_t *var,
-    nxt_str_t *str)
+nxt_var_interpreter(nxt_task_t *task, nxt_var_cache_t *cache, nxt_var_t *var,
+    nxt_str_t *str, void *ctx, nxt_bool_t logging)
 {
     u_char         *p, *src;
     size_t         length, last, next;
     nxt_str_t      *value, **part;
     nxt_uint_t     i;
-    nxt_bool_t     strz, logging;
     nxt_array_t    parts;
     nxt_var_sub_t  *subs;
 
-    if (nxt_var_is_const(var)) {
-        nxt_var_raw(var, str);
-        return;
-    }
-
-    if (nxt_slow_path(query->failed)) {
-        return;
-    }
-
     nxt_memzero(&parts, sizeof(nxt_array_t));
-    nxt_array_init(&parts, query->pool, sizeof(nxt_str_t *));
-
-    strz = (var->flags & NXT_VAR_STRZ) != 0;
-    logging = (var->flags & NXT_VAR_LOGGING) != 0;
+    nxt_array_init(&parts, cache->pool, sizeof(nxt_str_t *));
 
     subs = nxt_var_subs(var);
 
     length = var->length;
 
     for (i = 0; i < var->vars; i++) {
-        value = nxt_var_cache_value(task, query, subs[i].index);
+        value = nxt_var_cache_value(task, cache, subs[i].index, ctx);
         if (nxt_slow_path(value == NULL)) {
-            goto fail;
+            return NXT_ERROR;
         }
 
         part = nxt_array_add(&parts);
         if (nxt_slow_path(part == NULL)) {
-            goto fail;
+            return NXT_ERROR;
         }
 
         *part = value;
@@ -603,9 +541,9 @@ nxt_var_query(nxt_task_t *task, nxt_var_query_t *query, nxt_var_t *var,
         }
     }
 
-    p = nxt_mp_nget(query->pool, length + strz);
+    p = nxt_mp_nget(cache->pool, length);
     if (nxt_slow_path(p == NULL)) {
-        goto fail;
+        return NXT_ERROR;
     }
 
     str->length = length;
@@ -636,45 +574,5 @@ nxt_var_query(nxt_task_t *task, nxt_var_query_t *query, nxt_var_t *var,
         p = nxt_cpymem(p, &src[last], var->length - last);
     }
 
-    if (strz) {
-        *p = '\0';
-    }
-
-    nxt_debug(task, "var: \"%*s\" -> \"%V\"", length, src, str);
-
-    return;
-
-fail:
-
-    query->failed = 1;
-}
-
-
-void
-nxt_var_query_resolve(nxt_task_t *task, nxt_var_query_t *query, void *data,
-    nxt_work_handler_t ready, nxt_work_handler_t error)
-{
-    query->data = data;
-    query->ready = ready;
-    query->error = error;
-
-    if (query->waiting == 0) {
-        nxt_work_queue_add(&task->thread->engine->fast_work_queue,
-                           query->failed ? query->error : query->ready,
-                           task, query->ctx, query->data);
-    }
-}
-
-
-void
-nxt_var_query_handle(nxt_task_t *task, nxt_var_query_t *query,
-    nxt_bool_t failed)
-{
-    query->failed |= failed;
-
-    if (--query->waiting == 0) {
-        nxt_work_queue_add(&task->thread->engine->fast_work_queue,
-                           query->failed ? query->error : query->ready,
-                           task, query->ctx, query->data);
-    }
+    return NXT_OK;
 }
diff --git a/src/nxt_var.h b/src/nxt_var.h
index 34c8857a..2c6f13bd 100644
--- a/src/nxt_var.h
+++ b/src/nxt_var.h
@@ -32,10 +32,11 @@ typedef struct {
 } nxt_var_field_t;
 
 
-typedef enum {
-    NXT_VAR_STRZ       = 1 << 0,
-    NXT_VAR_LOGGING    = 1 << 1,
-} nxt_var_flags_t;
+typedef struct {
+    nxt_mp_t                *pool;
+    nxt_lvlhsh_t            hash;
+    nxt_str_t               *spare;
+} nxt_var_cache_t;
 
 
 nxt_inline nxt_bool_t
@@ -50,21 +51,11 @@ nxt_int_t nxt_var_index_init(void);
 
 nxt_var_field_t *nxt_var_field_get(nxt_array_t *fields, uint16_t index);
 
-nxt_var_t *nxt_var_compile(nxt_str_t *str, nxt_mp_t *mp, nxt_array_t *fields,
-    nxt_var_flags_t flags);
+nxt_var_t *nxt_var_compile(nxt_str_t *str, nxt_mp_t *mp, nxt_array_t *fields);
 nxt_int_t nxt_var_test(nxt_str_t *str, nxt_array_t *fields, u_char *error);
 
-nxt_bool_t nxt_var_is_const(nxt_var_t *var);
-void nxt_var_raw(nxt_var_t *var, nxt_str_t *str);
-
-nxt_int_t nxt_var_query_init(nxt_var_query_t **query_p, void *ctx,
-    nxt_mp_t *mp);
-void nxt_var_query(nxt_task_t *task, nxt_var_query_t *query,
-    nxt_var_t *var, nxt_str_t *str);
-void nxt_var_query_resolve(nxt_task_t *task, nxt_var_query_t *query, void *data,
-    nxt_work_handler_t ready, nxt_work_handler_t error);
-void nxt_var_query_handle(nxt_task_t *task, nxt_var_query_t *query,
-    nxt_bool_t failed);
+nxt_int_t nxt_var_interpreter(nxt_task_t *task, nxt_var_cache_t *cache,
+    nxt_var_t *var, nxt_str_t *str, void *ctx, nxt_bool_t logging);
 
 
 #endif /* _NXT_VAR_H_INCLUDED_ */