1 files changed, 335 insertions, 0 deletions

diff --git a/src/core/lib/slice/slice_intern.cc b/src/core/lib/slice/slice_intern.cc
new file mode 100644
index 0000000000..1ea9a2aa67
--- /dev/null
+++ b/src/core/lib/slice/slice_intern.cc
@@ -0,0 +1,335 @@
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/slice/slice_internal.h"
+
+#include <inttypes.h>
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+
+#include "src/core/lib/iomgr/iomgr_internal.h" /* for iomgr_abort_on_leaks() */
+#include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/slice/slice_string_helpers.h"
+#include "src/core/lib/support/murmur_hash.h"
+#include "src/core/lib/transport/static_metadata.h"
+
+#define LOG2_SHARD_COUNT 5
+#define SHARD_COUNT (1 << LOG2_SHARD_COUNT)
+#define INITIAL_SHARD_CAPACITY 8
+
+#define TABLE_IDX(hash, capacity) (((hash) >> LOG2_SHARD_COUNT) % (capacity))
+#define SHARD_IDX(hash) ((hash) & ((1 << LOG2_SHARD_COUNT) - 1))
+
+typedef struct interned_slice_refcount {
+  grpc_slice_refcount base;
+  grpc_slice_refcount sub;
+  size_t length;
+  gpr_atm refcnt;
+  uint32_t hash;
+  struct interned_slice_refcount *bucket_next;
+} interned_slice_refcount;
+
+typedef struct slice_shard {
+  gpr_mu mu;
+  interned_slice_refcount **strs;
+  size_t count;
+  size_t capacity;
+} slice_shard;
+
+/* hash seed: decided at initialization time */
+static uint32_t g_hash_seed;
+static int g_forced_hash_seed = 0;
+
+static slice_shard g_shards[SHARD_COUNT];
+
+typedef struct {
+  uint32_t hash;
+  uint32_t idx;
+} static_metadata_hash_ent;
+
+static static_metadata_hash_ent
+    static_metadata_hash[4 * GRPC_STATIC_MDSTR_COUNT];
+static uint32_t max_static_metadata_hash_probe;
+static uint32_t static_metadata_hash_values[GRPC_STATIC_MDSTR_COUNT];
+
+static void interned_slice_ref(void *p) {
+  interned_slice_refcount *s = (interned_slice_refcount *)p;
+  GPR_ASSERT(gpr_atm_no_barrier_fetch_add(&s->refcnt, 1) > 0);
+}
+
+static void interned_slice_destroy(interned_slice_refcount *s) {
+  slice_shard *shard = &g_shards[SHARD_IDX(s->hash)];
+  gpr_mu_lock(&shard->mu);
+  GPR_ASSERT(0 == gpr_atm_no_barrier_load(&s->refcnt));
+  interned_slice_refcount **prev_next;
+  interned_slice_refcount *cur;
+  for (prev_next = &shard->strs[TABLE_IDX(s->hash, shard->capacity)],
+      cur = *prev_next;
+       cur != s; prev_next = &cur->bucket_next, cur = cur->bucket_next)
+    ;
+  *prev_next = cur->bucket_next;
+  shard->count--;
+  gpr_free(s);
+  gpr_mu_unlock(&shard->mu);
+}
+
+static void interned_slice_unref(grpc_exec_ctx *exec_ctx, void *p) {
+  interned_slice_refcount *s = (interned_slice_refcount *)p;
+  if (1 == gpr_atm_full_fetch_add(&s->refcnt, -1)) {
+    interned_slice_destroy(s);
+  }
+}
+
+static void interned_slice_sub_ref(void *p) {
+  interned_slice_ref(((char *)p) - offsetof(interned_slice_refcount, sub));
+}
+
+static void interned_slice_sub_unref(grpc_exec_ctx *exec_ctx, void *p) {
+  interned_slice_unref(exec_ctx,
+                       ((char *)p) - offsetof(interned_slice_refcount, sub));
+}
+
+static uint32_t interned_slice_hash(grpc_slice slice) {
+  interned_slice_refcount *s = (interned_slice_refcount *)slice.refcount;
+  return s->hash;
+}
+
+static int interned_slice_eq(grpc_slice a, grpc_slice b) {
+  return a.refcount == b.refcount;
+}
+
+static const grpc_slice_refcount_vtable interned_slice_vtable = {
+    interned_slice_ref, interned_slice_unref, interned_slice_eq,
+    interned_slice_hash};
+static const grpc_slice_refcount_vtable interned_slice_sub_vtable = {
+    interned_slice_sub_ref, interned_slice_sub_unref,
+    grpc_slice_default_eq_impl, grpc_slice_default_hash_impl};
+
+static void grow_shard(slice_shard *shard) {
+  size_t capacity = shard->capacity * 2;
+  size_t i;
+  interned_slice_refcount **strtab;
+  interned_slice_refcount *s, *next;
+
+  GPR_TIMER_BEGIN("grow_strtab", 0);
+
+  strtab = (interned_slice_refcount **)gpr_zalloc(
+      sizeof(interned_slice_refcount *) * capacity);
+
+  for (i = 0; i < shard->capacity; i++) {
+    for (s = shard->strs[i]; s; s = next) {
+      size_t idx = TABLE_IDX(s->hash, capacity);
+      next = s->bucket_next;
+      s->bucket_next = strtab[idx];
+      strtab[idx] = s;
+    }
+  }
+
+  gpr_free(shard->strs);
+  shard->strs = strtab;
+  shard->capacity = capacity;
+
+  GPR_TIMER_END("grow_strtab", 0);
+}
+
+static grpc_slice materialize(interned_slice_refcount *s) {
+  grpc_slice slice;
+  slice.refcount = &s->base;
+  slice.data.refcounted.bytes = (uint8_t *)(s + 1);
+  slice.data.refcounted.length = s->length;
+  return slice;
+}
+
+uint32_t grpc_slice_default_hash_impl(grpc_slice s) {
+  return gpr_murmur_hash3(GRPC_SLICE_START_PTR(s), GRPC_SLICE_LENGTH(s),
+                          g_hash_seed);
+}
+
+uint32_t grpc_static_slice_hash(grpc_slice s) {
+  return static_metadata_hash_values[GRPC_STATIC_METADATA_INDEX(s)];
+}
+
+int grpc_static_slice_eq(grpc_slice a, grpc_slice b) {
+  return GRPC_STATIC_METADATA_INDEX(a) == GRPC_STATIC_METADATA_INDEX(b);
+}
+
+uint32_t grpc_slice_hash(grpc_slice s) {
+  return s.refcount == NULL ? grpc_slice_default_hash_impl(s)
+                            : s.refcount->vtable->hash(s);
+}
+
+grpc_slice grpc_slice_maybe_static_intern(grpc_slice slice,
+                                          bool *returned_slice_is_different) {
+  if (GRPC_IS_STATIC_METADATA_STRING(slice)) {
+    return slice;
+  }
+
+  uint32_t hash = grpc_slice_hash(slice);
+  for (uint32_t i = 0; i <= max_static_metadata_hash_probe; i++) {
+    static_metadata_hash_ent ent =
+        static_metadata_hash[(hash + i) % GPR_ARRAY_SIZE(static_metadata_hash)];
+    if (ent.hash == hash && ent.idx < GRPC_STATIC_MDSTR_COUNT &&
+        grpc_slice_eq(grpc_static_slice_table[ent.idx], slice)) {
+      *returned_slice_is_different = true;
+      return grpc_static_slice_table[ent.idx];
+    }
+  }
+
+  return slice;
+}
+
+bool grpc_slice_is_interned(grpc_slice slice) {
+  return (slice.refcount && slice.refcount->vtable == &interned_slice_vtable) ||
+         GRPC_IS_STATIC_METADATA_STRING(slice);
+}
+
+grpc_slice grpc_slice_intern(grpc_slice slice) {
+  GPR_TIMER_BEGIN("grpc_slice_intern", 0);
+  if (GRPC_IS_STATIC_METADATA_STRING(slice)) {
+    GPR_TIMER_END("grpc_slice_intern", 0);
+    return slice;
+  }
+
+  uint32_t hash = grpc_slice_hash(slice);
+  for (uint32_t i = 0; i <= max_static_metadata_hash_probe; i++) {
+    static_metadata_hash_ent ent =
+        static_metadata_hash[(hash + i) % GPR_ARRAY_SIZE(static_metadata_hash)];
+    if (ent.hash == hash && ent.idx < GRPC_STATIC_MDSTR_COUNT &&
+        grpc_slice_eq(grpc_static_slice_table[ent.idx], slice)) {
+      GPR_TIMER_END("grpc_slice_intern", 0);
+      return grpc_static_slice_table[ent.idx];
+    }
+  }
+
+  interned_slice_refcount *s;
+  slice_shard *shard = &g_shards[SHARD_IDX(hash)];
+
+  gpr_mu_lock(&shard->mu);
+
+  /* search for an existing string */
+  size_t idx = TABLE_IDX(hash, shard->capacity);
+  for (s = shard->strs[idx]; s; s = s->bucket_next) {
+    if (s->hash == hash && grpc_slice_eq(slice, materialize(s))) {
+      if (gpr_atm_no_barrier_fetch_add(&s->refcnt, 1) == 0) {
+        /* If we get here, we've added a ref to something that was about to
+         * die - drop it immediately.
+         * The *only* possible path here (given the shard mutex) should be to
+         * drop from one ref back to zero - assert that with a CAS */
+        GPR_ASSERT(gpr_atm_rel_cas(&s->refcnt, 1, 0));
+        /* and treat this as if we were never here... sshhh */
+      } else {
+        gpr_mu_unlock(&shard->mu);
+        GPR_TIMER_END("grpc_slice_intern", 0);
+        return materialize(s);
+      }
+    }
+  }
+
+  /* not found: create a new string */
+  /* string data goes after the internal_string header */
+  s = (interned_slice_refcount *)gpr_malloc(sizeof(*s) +
+                                            GRPC_SLICE_LENGTH(slice));
+  gpr_atm_rel_store(&s->refcnt, 1);
+  s->length = GRPC_SLICE_LENGTH(slice);
+  s->hash = hash;
+  s->base.vtable = &interned_slice_vtable;
+  s->base.sub_refcount = &s->sub;
+  s->sub.vtable = &interned_slice_sub_vtable;
+  s->sub.sub_refcount = &s->sub;
+  s->bucket_next = shard->strs[idx];
+  shard->strs[idx] = s;
+  memcpy(s + 1, GRPC_SLICE_START_PTR(slice), GRPC_SLICE_LENGTH(slice));
+
+  shard->count++;
+
+  if (shard->count > shard->capacity * 2) {
+    grow_shard(shard);
+  }
+
+  gpr_mu_unlock(&shard->mu);
+
+  GPR_TIMER_END("grpc_slice_intern", 0);
+  return materialize(s);
+}
+
+void grpc_test_only_set_slice_hash_seed(uint32_t seed) {
+  g_hash_seed = seed;
+  g_forced_hash_seed = 1;
+}
+
+void grpc_slice_intern_init(void) {
+  if (!g_forced_hash_seed) {
+    g_hash_seed = (uint32_t)gpr_now(GPR_CLOCK_REALTIME).tv_nsec;
+  }
+  for (size_t i = 0; i < SHARD_COUNT; i++) {
+    slice_shard *shard = &g_shards[i];
+    gpr_mu_init(&shard->mu);
+    shard->count = 0;
+    shard->capacity = INITIAL_SHARD_CAPACITY;
+    shard->strs = (interned_slice_refcount **)gpr_zalloc(sizeof(*shard->strs) *
+                                                         shard->capacity);
+  }
+  for (size_t i = 0; i < GPR_ARRAY_SIZE(static_metadata_hash); i++) {
+    static_metadata_hash[i].hash = 0;
+    static_metadata_hash[i].idx = GRPC_STATIC_MDSTR_COUNT;
+  }
+  max_static_metadata_hash_probe = 0;
+  for (size_t i = 0; i < GRPC_STATIC_MDSTR_COUNT; i++) {
+    static_metadata_hash_values[i] =
+        grpc_slice_default_hash_impl(grpc_static_slice_table[i]);
+    for (size_t j = 0; j < GPR_ARRAY_SIZE(static_metadata_hash); j++) {
+      size_t slot = (static_metadata_hash_values[i] + j) %
+                    GPR_ARRAY_SIZE(static_metadata_hash);
+      if (static_metadata_hash[slot].idx == GRPC_STATIC_MDSTR_COUNT) {
+        static_metadata_hash[slot].hash = static_metadata_hash_values[i];
+        static_metadata_hash[slot].idx = (uint32_t)i;
+        if (j > max_static_metadata_hash_probe) {
+          max_static_metadata_hash_probe = (uint32_t)j;
+        }
+        break;
+      }
+    }
+  }
+}
+
+void grpc_slice_intern_shutdown(void) {
+  for (size_t i = 0; i < SHARD_COUNT; i++) {
+    slice_shard *shard = &g_shards[i];
+    gpr_mu_destroy(&shard->mu);
+    /* TODO(ctiller): GPR_ASSERT(shard->count == 0); */
+    if (shard->count != 0) {
+      gpr_log(GPR_DEBUG, "WARNING: %" PRIuPTR " metadata strings were leaked",
+              shard->count);
+      for (size_t j = 0; j < shard->capacity; j++) {
+        for (interned_slice_refcount *s = shard->strs[j]; s;
+             s = s->bucket_next) {
+          char *text =
+              grpc_dump_slice(materialize(s), GPR_DUMP_HEX | GPR_DUMP_ASCII);
+          gpr_log(GPR_DEBUG, "LEAKED: %s", text);
+          gpr_free(text);
+        }
+      }
+      if (grpc_iomgr_abort_on_leaks()) {
+        abort();
+      }
+    }
+    gpr_free(shard->strs);
+  }
+}