new file mode 100644
--- /dev/null
+++ b/src/http/ngx_http_variables.c
@@ -0,0 +1,338 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+#include <ngx_http.h>
+
+
+#define NGX_HTTP_VARS_HASH_PRIME  29
+
+#define ngx_http_vars_hash_key(key, vn)                                      \
+    {                                                                        \
+        ngx_uint_t  n;                                                       \
+        for (key = 0, n = 0; n < (vn)->len; n++) {                           \
+            key += (vn)->data[n];                                            \
+        }                                                                    \
+        key %= NGX_HTTP_VARS_HASH_PRIME;                                     \
+    }
+
+
+static ngx_http_variable_value_t *
+    ngx_http_variable_header(ngx_http_request_t *r, uintptr_t data);
+static ngx_http_variable_value_t *
+    ngx_http_variable_unknown_header(ngx_http_request_t *r, ngx_str_t *var);
+static ngx_http_variable_value_t *
+    ngx_http_variable_remote_addr(ngx_http_request_t *r, uintptr_t data);
+static ngx_http_variable_value_t *
+    ngx_http_variable_uri(ngx_http_request_t *r, uintptr_t data);
+static ngx_http_variable_value_t *
+    ngx_http_variable_query_string(ngx_http_request_t *r, uintptr_t data);
+
+
+static ngx_array_t  *ngx_http_core_variables_hash;
+
+
+static ngx_http_core_variable_t  ngx_http_core_variables[] = {
+
+    { ngx_string("HTTP_HOST"), ngx_http_variable_header,
+      offsetof(ngx_http_headers_in_t, host) },
+
+    { ngx_string("HTTP_USER_AGENT"), ngx_http_variable_header,
+      offsetof(ngx_http_headers_in_t, user_agent) },
+
+    { ngx_string("HTTP_REFERER"), ngx_http_variable_header,
+      offsetof(ngx_http_headers_in_t, referer) },
+
+#if (NGX_HTTP_GZIP)
+    { ngx_string("HTTP_VIA"), ngx_http_variable_header,
+      offsetof(ngx_http_headers_in_t, via) },
+#endif
+
+#if (NGX_HTTP_PROXY)
+    { ngx_string("HTTP_X_FORWARDED_FOR"), ngx_http_variable_header,
+      offsetof(ngx_http_headers_in_t, x_forwarded_for) },
+#endif
+
+    { ngx_string("REMOTE_ADDR"), ngx_http_variable_remote_addr, 0 },
+
+    { ngx_string("DOCUMENT_URI"), ngx_http_variable_uri, 0 },
+
+    { ngx_string("QUERY_STRING"), ngx_http_variable_query_string, 0 },
+
+    { ngx_null_string, NULL, 0 }
+};
+
+
+ngx_http_variable_t *
+ngx_http_add_variable(ngx_conf_t *cf)
+{
+    ngx_http_variable_t        *var;
+    ngx_http_core_main_conf_t  *cmcf;
+
+    cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);
+
+    if (cmcf->variables.elts == NULL) {
+        if (ngx_array_init(&cmcf->variables, cf->pool, 4,
+                           sizeof(ngx_http_variable_t)) == NGX_ERROR)
+        {
+            return NULL;
+        }
+    }
+
+    if (!(var = ngx_array_push(&cmcf->variables))) {
+        return NULL;
+    }
+
+    var->index = cmcf->variables.nelts - 1;
+
+    return var;
+}
+
+
+ngx_http_variable_value_t *
+ngx_http_get_indexed_variable(ngx_http_request_t *r, ngx_uint_t index)
+{
+    ngx_http_variable_t        *var;
+    ngx_http_core_main_conf_t  *cmcf;
+
+    /* TODO: cached variables */
+
+    cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
+
+    if (cmcf->variables.elts == NULL || cmcf->variables.nelts <= index) {
+        ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
+                      "unknown variable index: %d", index);
+        return NULL;
+    }
+
+    var = cmcf->variables.elts;
+
+    return var[index].handler(r, var[index].data);
+}
+
+
+ngx_int_t
+ngx_http_get_variable_index(ngx_http_core_main_conf_t *cmcf, ngx_str_t *name)
+{
+    ngx_uint_t            i;
+    ngx_http_variable_t  *var;
+
+    var = cmcf->variables.elts;
+    for (i = 0; i < cmcf->variables.nelts; i++) {
+        if (var[i].name.len != name->len) {
+            continue;
+        }
+
+        if (ngx_strncasecmp(var[i].name.data, name->data, name->len) == 0) {
+            return var[i].index;
+        }
+    }
+
+    return -1;
+}
+
+
+ngx_http_variable_value_t *
+ngx_http_get_variable(ngx_http_request_t *r, ngx_str_t *name)
+{
+    ngx_int_t                   index;
+    ngx_uint_t                  i, key;
+    ngx_http_core_variable_t   *var;
+    ngx_http_core_main_conf_t  *cmcf;
+
+    cmcf = ngx_http_get_module_main_conf(r, ngx_http_core_module);
+
+    index = ngx_http_get_variable_index(cmcf, name);
+
+    if (index != -1) {
+        return ngx_http_get_indexed_variable(r, index);
+    }
+
+    ngx_http_vars_hash_key(key, name);
+
+    var = ngx_http_core_variables_hash[key].elts;
+    for (i = 0; i < ngx_http_core_variables_hash[key].nelts; i++) {
+
+        if (var[i].name.len != name->len
+            || ngx_strncasecmp(var[i].name.data, name->data, name->len) != 0)
+        {
+            continue;
+        }
+
+        return var[i].handler(r, var[i].data);
+    }
+
+    if (ngx_strncasecmp(name->data, "HTTP_", 5) != 0) {
+        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                      "unknown \"%V\" variable", name);
+        return NGX_HTTP_VARIABLE_NOT_FOUND;
+    }
+
+    return ngx_http_variable_unknown_header(r, name);
+}
+
+
+static ngx_http_variable_value_t *
+ngx_http_variable_header(ngx_http_request_t *r, uintptr_t data)
+{
+    ngx_table_elt_t            *h;
+    ngx_http_variable_value_t  *v;
+
+    h = *(ngx_table_elt_t **) ((char *) &r->headers_in + data);
+
+    if (h == NULL) {
+        return NGX_HTTP_VARIABLE_NOT_FOUND;
+    }
+
+    if (!(v = ngx_palloc(r->pool, sizeof(ngx_http_variable_value_t)))) {
+        return NULL;
+    }
+
+    v->value = 0;
+    v->text = h->value;
+
+    return v;
+}
+
+
+static ngx_http_variable_value_t *
+ngx_http_variable_unknown_header(ngx_http_request_t *r, ngx_str_t *var)
+{
+    u_char                      ch;
+    ngx_uint_t                  i, n;
+    ngx_list_part_t            *part;
+    ngx_table_elt_t            *header;
+    ngx_http_variable_value_t  *v;
+
+    part = &r->headers_in.headers.part;
+    header = part->elts;
+
+    for (i = 0; /* void */ ; i++) {
+
+        if (i >= part->nelts) {
+            if (part->next == NULL) {
+                break;
+            }
+
+            part = part->next;
+            header = part->elts;
+            i = 0;
+        }
+
+        for (n = 0; n + 5 < var->len && n < header[i].key.len; n++)
+        {
+            ch = header[i].key.data[n];
+
+            if (ch >= 'a' && ch <= 'z') {
+                ch &= ~0x20;
+
+            } else if (ch == '-') {
+                ch = '_';
+            }
+
+            if (var->data[n + 5] != ch) {
+                break;
+            }
+        }
+
+        if (n + 5 == var->len) {
+            if (!(v = ngx_palloc(r->pool, sizeof(ngx_http_variable_value_t)))) {
+                return NULL;
+            }
+
+            v->value = 0;
+            v->text = header[i].value;
+            return v;
+        }
+    }
+
+    return NGX_HTTP_VARIABLE_NOT_FOUND;
+}
+
+
+static ngx_http_variable_value_t *
+ngx_http_variable_remote_addr(ngx_http_request_t *r, uintptr_t data)
+{
+    ngx_http_variable_value_t  *v;
+
+    if (!(v = ngx_palloc(r->pool, sizeof(ngx_http_variable_value_t)))) {
+        return NULL;
+    }
+
+    v->value = 0;
+    v->text = r->connection->addr_text;
+
+    return v;
+}
+
+
+static ngx_http_variable_value_t *
+ngx_http_variable_uri(ngx_http_request_t *r, uintptr_t data)
+{
+    ngx_http_variable_value_t  *v;
+
+    if (!(v = ngx_palloc(r->pool, sizeof(ngx_http_variable_value_t)))) {
+        return NULL;
+    }
+
+    v->value = 0;
+    v->text = r->uri;
+
+    return v;
+}
+
+
+static ngx_http_variable_value_t *
+ngx_http_variable_query_string(ngx_http_request_t *r, uintptr_t data)
+{
+    ngx_http_variable_value_t  *v;
+
+    if (!(v = ngx_palloc(r->pool, sizeof(ngx_http_variable_value_t)))) {
+        return NULL;
+    }
+
+    v->value = 0;
+    v->text = r->args;
+
+    return v;
+}
+
+
+ngx_int_t
+ngx_http_core_variables_init(ngx_cycle_t *cycle)
+{
+    ngx_uint_t                 i, key;
+    ngx_http_core_variable_t  *var, *v;
+
+    ngx_http_core_variables_hash = ngx_palloc(cycle->pool,
+                                              NGX_HTTP_VARS_HASH_PRIME
+                                              * sizeof(ngx_array_t));
+    if (ngx_http_core_variables_hash == NULL) {
+        return NGX_ERROR;
+    }
+
+    for (i = 0; i < NGX_HTTP_VARS_HASH_PRIME; i++) {
+        if (ngx_array_init(&ngx_http_core_variables_hash[i], cycle->pool, 4,
+                           sizeof(ngx_http_core_variable_t)) == NGX_ERROR)
+        {
+            return NGX_ERROR;
+        }
+    }
+
+    for (var = ngx_http_core_variables; var->name.len; var++) {
+        ngx_http_vars_hash_key(key, &var->name);
+
+        if (!(v = ngx_array_push(&ngx_http_core_variables_hash[key]))) {
+            return NGX_ERROR;
+        }
+
+        *v = *var;
+    }
+
+    return NGX_OK;
+}