Initial checkin of gRPC to third_party/

third_party/grpc/src/core/census/context.c

Index: third_party/grpc/src/core/census/context.c
diff --git a/third_party/grpc/src/core/census/context.c b/third_party/grpc/src/core/census/context.c
new file mode 100644
index 0000000000000000000000000000000000000000..89b8ee0b399dbb7a403f07075b13b9da9664c545
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+++ b/third_party/grpc/src/core/census/context.c
@@ -0,0 +1,509 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/census.h>
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/port_platform.h>
+#include <grpc/support/useful.h>
+#include <stdbool.h>
+#include <string.h>
+#include "src/core/support/string.h"
+
+// Functions in this file support the public context API, including
+// encoding/decoding as part of context propagation across RPC's. The overall
+// requirements (in approximate priority order) for the
+// context representation:
+// 1. Efficient conversion to/from wire format
+// 2. Minimal bytes used on-wire
+// 3. Efficient context creation
+// 4. Efficient lookup of tag value for a key
+// 5. Efficient iteration over tags
+// 6. Minimal memory footprint
+//
+// Notes on tradeoffs/decisions:
+// * tag includes 1 byte length of key, as well as nil-terminating byte. These
+//   are to aid in efficient parsing and the ability to directly return key
+//   strings. This is more important than saving a single byte/tag on the wire.
+// * The wire encoding uses only single byte values. This eliminates the need
+//   to handle endian-ness conversions. It also means there is a hard upper
+//   limit of 255 for both CENSUS_MAX_TAG_KV_LEN and CENSUS_MAX_PROPAGATED_TAGS.
+// * Keep all tag information (keys/values/flags) in a single memory buffer,
+//   that can be directly copied to the wire.
+
+// min and max valid chars in tag keys and values. All printable ASCII is OK.
+#define MIN_VALID_TAG_CHAR 32   // ' '
+#define MAX_VALID_TAG_CHAR 126  // '~'
+
+// Structure representing a set of tags. Essentially a count of number of tags
+// present, and pointer to a chunk of memory that contains the per-tag details.
+struct tag_set {
+  int ntags;        // number of tags.
+  int ntags_alloc;  // ntags + number of deleted tags (total number of tags
+  // in all of kvm). This will always be == ntags, except during the process
+  // of building a new tag set.
+  size_t kvm_size;  // number of bytes allocated for key/value storage.
+  size_t kvm_used;  // number of bytes of used key/value memory
+  char *kvm;        // key/value memory. Consists of repeated entries of:
+  //   Offset  Size  Description
+  //     0      1    Key length, including trailing 0. (K)
+  //     1      1    Value length, including trailing 0 (V)
+  //     2      1    Flags
+  //     3      K    Key bytes
+  //     3 + K  V    Value bytes
+  //
+  // We refer to the first 3 entries as the 'tag header'. If extra values are
+  // introduced in the header, you will need to modify the TAG_HEADER_SIZE
+  // constant, the raw_tag structure (and everything that uses it) and the
+  // encode/decode functions appropriately.
+};
+
+// Number of bytes in tag header.
+#define TAG_HEADER_SIZE 3  // key length (1) + value length (1) + flags (1)
+// Offsets to tag header entries.
+#define KEY_LEN_OFFSET 0
+#define VALUE_LEN_OFFSET 1
+#define FLAG_OFFSET 2
+
+// raw_tag represents the raw-storage form of a tag in the kvm of a tag_set.
+struct raw_tag {
+  uint8_t key_len;
+  uint8_t value_len;
+  uint8_t flags;
+  char *key;
+  char *value;
+};
+
+// Use a reserved flag bit for indication of deleted tag.
+#define CENSUS_TAG_DELETED CENSUS_TAG_RESERVED
+#define CENSUS_TAG_IS_DELETED(flags) (flags & CENSUS_TAG_DELETED)
+
+// Primary representation of a context. Composed of 2 underlying tag_set
+// structs, one each for propagated and local (non-propagated) tags. This is
+// to efficiently support tag encoding/decoding.
+// TODO(aveitch): need to add tracing id's/structure.
+struct census_context {
+  struct tag_set tags[2];
+  census_context_status status;
+};
+
+// Indices into the tags member of census_context
+#define PROPAGATED_TAGS 0
+#define LOCAL_TAGS 1
+
+// Validate (check all characters are in range and size is less than limit) a
+// key or value string. Returns 0 if the string is invalid, or the length
+// (including terminator) if valid.
+static size_t validate_tag(const char *kv) {
+  size_t len = 1;
+  char ch;
+  while ((ch = *kv++) != 0) {
+    if (ch < MIN_VALID_TAG_CHAR || ch > MAX_VALID_TAG_CHAR) {
+      return 0;
+    }
+    len++;
+  }
+  if (len > CENSUS_MAX_TAG_KV_LEN) {
+    return 0;
+  }
+  return len;
+}
+
+// Extract a raw tag given a pointer (raw) to the tag header. Allow for some
+// extra bytes in the tag header (see encode/decode functions for usage: this
+// allows for future expansion of the tag header).
+static char *decode_tag(struct raw_tag *tag, char *header, int offset) {
+  tag->key_len = (uint8_t)(*header++);
+  tag->value_len = (uint8_t)(*header++);
+  tag->flags = (uint8_t)(*header++);
+  header += offset;
+  tag->key = header;
+  header += tag->key_len;
+  tag->value = header;
+  return header + tag->value_len;
+}
+
+// Make a copy (in 'to') of an existing tag_set.
+static void tag_set_copy(struct tag_set *to, const struct tag_set *from) {
+  memcpy(to, from, sizeof(struct tag_set));
+  to->kvm = gpr_malloc(to->kvm_size);
+  memcpy(to->kvm, from->kvm, from->kvm_used);
+}
+
+// Delete a tag from a tag_set, if it exists (returns true if it did).
+static bool tag_set_delete_tag(struct tag_set *tags, const char *key,
+                               size_t key_len) {
+  char *kvp = tags->kvm;
+  for (int i = 0; i < tags->ntags_alloc; i++) {
+    uint8_t *flags = (uint8_t *)(kvp + FLAG_OFFSET);
+    struct raw_tag tag;
+    kvp = decode_tag(&tag, kvp, 0);
+    if (CENSUS_TAG_IS_DELETED(tag.flags)) continue;
+    if ((key_len == tag.key_len) && (memcmp(key, tag.key, key_len) == 0)) {
+      *flags |= CENSUS_TAG_DELETED;
+      tags->ntags--;
+      return true;
+    }
+  }
+  return false;
+}
+
+// Delete a tag from a context, return true if it existed.
+static bool context_delete_tag(census_context *context, const census_tag *tag,
+                               size_t key_len) {
+  return (
+      tag_set_delete_tag(&context->tags[LOCAL_TAGS], tag->key, key_len) ||
+      tag_set_delete_tag(&context->tags[PROPAGATED_TAGS], tag->key, key_len));
+}
+
+// Add a tag to a tag_set. Return true on success, false if the tag could
+// not be added because of constraints on tag set size. This function should
+// not be called if the tag may already exist (in a non-deleted state) in
+// the tag_set, as that would result in two tags with the same key.
+static bool tag_set_add_tag(struct tag_set *tags, const census_tag *tag,
+                            size_t key_len, size_t value_len) {
+  if (tags->ntags == CENSUS_MAX_PROPAGATED_TAGS) {
+    return false;
+  }
+  const size_t tag_size = key_len + value_len + TAG_HEADER_SIZE;
+  if (tags->kvm_used + tag_size > tags->kvm_size) {
+    // allocate new memory if needed
+    tags->kvm_size += 2 * CENSUS_MAX_TAG_KV_LEN + TAG_HEADER_SIZE;
+    char *new_kvm = gpr_malloc(tags->kvm_size);
+    memcpy(new_kvm, tags->kvm, tags->kvm_used);
+    gpr_free(tags->kvm);
+    tags->kvm = new_kvm;
+  }
+  char *kvp = tags->kvm + tags->kvm_used;
+  *kvp++ = (char)key_len;
+  *kvp++ = (char)value_len;
+  // ensure reserved flags are not used.
+  *kvp++ = (char)(tag->flags & (CENSUS_TAG_PROPAGATE | CENSUS_TAG_STATS));
+  memcpy(kvp, tag->key, key_len);
+  kvp += key_len;
+  memcpy(kvp, tag->value, value_len);
+  tags->kvm_used += tag_size;
+  tags->ntags++;
+  tags->ntags_alloc++;
+  return true;
+}
+
+// Add/modify/delete a tag to/in a context. Caller must validate that tag key
+// etc. are valid.
+static void context_modify_tag(census_context *context, const census_tag *tag,
+                               size_t key_len, size_t value_len) {
+  // First delete the tag if it is already present.
+  bool deleted = context_delete_tag(context, tag, key_len);
+  bool added = false;
+  if (CENSUS_TAG_IS_PROPAGATED(tag->flags)) {
+    added = tag_set_add_tag(&context->tags[PROPAGATED_TAGS], tag, key_len,
+                            value_len);
+  } else {
+    added =
+        tag_set_add_tag(&context->tags[LOCAL_TAGS], tag, key_len, value_len);
+  }
+
+  if (deleted) {
+    context->status.n_modified_tags++;
+  } else {
+    if (added) {
+      context->status.n_added_tags++;
+    } else {
+      context->status.n_ignored_tags++;
+    }
+  }
+}
+
+// Remove memory used for deleted tags from a tag set. Basic algorithm:
+// 1) Walk through tag set to find first deleted tag. Record where it is.
+// 2) Find the next not-deleted tag. Copy all of kvm from there to the end
+//    "over" the deleted tags
+// 3) repeat #1 and #2 until we have seen all tags
+// 4) if we are still looking for a not-deleted tag, then all the end portion
+//    of the kvm is deleted. Just reduce the used amount of memory by the
+//    appropriate amount.
+static void tag_set_flatten(struct tag_set *tags) {
+  if (tags->ntags == tags->ntags_alloc) return;
+  bool found_deleted = false;  // found a deleted tag.
+  char *kvp = tags->kvm;
+  char *dbase = NULL;  // record location of deleted tag
+  for (int i = 0; i < tags->ntags_alloc; i++) {
+    struct raw_tag tag;
+    char *next_kvp = decode_tag(&tag, kvp, 0);
+    if (found_deleted) {
+      if (!CENSUS_TAG_IS_DELETED(tag.flags)) {
+        ptrdiff_t reduce = kvp - dbase;  // #bytes in deleted tags
+        GPR_ASSERT(reduce > 0);
+        ptrdiff_t copy_size = tags->kvm + tags->kvm_used - kvp;
+        GPR_ASSERT(copy_size > 0);
+        memmove(dbase, kvp, (size_t)copy_size);
+        tags->kvm_used -= (size_t)reduce;
+        next_kvp -= reduce;
+        found_deleted = false;
+      }
+    } else {
+      if (CENSUS_TAG_IS_DELETED(tag.flags)) {
+        dbase = kvp;
+        found_deleted = true;
+      }
+    }
+    kvp = next_kvp;
+  }
+  if (found_deleted) {
+    GPR_ASSERT(dbase > tags->kvm);
+    tags->kvm_used = (size_t)(dbase - tags->kvm);
+  }
+  tags->ntags_alloc = tags->ntags;
+}
+
+census_context *census_context_create(const census_context *base,
+                                      const census_tag *tags, int ntags,
+                                      census_context_status const **status) {
+  census_context *context = gpr_malloc(sizeof(census_context));
+  // If we are given a base, copy it into our new tag set. Otherwise set it
+  // to zero/NULL everything.
+  if (base == NULL) {
+    memset(context, 0, sizeof(census_context));
+  } else {
+    tag_set_copy(&context->tags[PROPAGATED_TAGS], &base->tags[PROPAGATED_TAGS]);
+    tag_set_copy(&context->tags[LOCAL_TAGS], &base->tags[LOCAL_TAGS]);
+    memset(&context->status, 0, sizeof(context->status));
+  }
+  // Walk over the additional tags and, for those that aren't invalid, modify
+  // the context to add/replace/delete as required.
+  for (int i = 0; i < ntags; i++) {
+    const census_tag *tag = &tags[i];
+    size_t key_len = validate_tag(tag->key);
+    // ignore the tag if it is invalid or too short.
+    if (key_len <= 1) {
+      context->status.n_invalid_tags++;
+    } else {
+      if (tag->value != NULL) {
+        size_t value_len = validate_tag(tag->value);
+        if (value_len != 0) {
+          context_modify_tag(context, tag, key_len, value_len);
+        } else {
+          context->status.n_invalid_tags++;
+        }
+      } else {
+        if (context_delete_tag(context, tag, key_len)) {
+          context->status.n_deleted_tags++;
+        }
+      }
+    }
+  }
+  // Remove any deleted tags, update status if needed, and return.
+  tag_set_flatten(&context->tags[PROPAGATED_TAGS]);
+  tag_set_flatten(&context->tags[LOCAL_TAGS]);
+  context->status.n_propagated_tags = context->tags[PROPAGATED_TAGS].ntags;
+  context->status.n_local_tags = context->tags[LOCAL_TAGS].ntags;
+  if (status) {
+    *status = &context->status;
+  }
+  return context;
+}
+
+const census_context_status *census_context_get_status(
+    const census_context *context) {
+  return &context->status;
+}
+
+void census_context_destroy(census_context *context) {
+  gpr_free(context->tags[PROPAGATED_TAGS].kvm);
+  gpr_free(context->tags[LOCAL_TAGS].kvm);
+  gpr_free(context);
+}
+
+void census_context_initialize_iterator(const census_context *context,
+                                        census_context_iterator *iterator) {
+  iterator->context = context;
+  iterator->index = 0;
+  if (context->tags[PROPAGATED_TAGS].ntags != 0) {
+    iterator->base = PROPAGATED_TAGS;
+    iterator->kvm = context->tags[PROPAGATED_TAGS].kvm;
+  } else if (context->tags[LOCAL_TAGS].ntags != 0) {
+    iterator->base = LOCAL_TAGS;
+    iterator->kvm = context->tags[LOCAL_TAGS].kvm;
+  } else {
+    iterator->base = -1;
+  }
+}
+
+int census_context_next_tag(census_context_iterator *iterator,
+                            census_tag *tag) {
+  if (iterator->base < 0) {
+    return 0;
+  }
+  struct raw_tag raw;
+  iterator->kvm = decode_tag(&raw, iterator->kvm, 0);
+  tag->key = raw.key;
+  tag->value = raw.value;
+  tag->flags = raw.flags;
+  if (++iterator->index == iterator->context->tags[iterator->base].ntags) {
+    do {
+      if (iterator->base == LOCAL_TAGS) {
+        iterator->base = -1;
+        return 1;
+      }
+    } while (iterator->context->tags[++iterator->base].ntags == 0);
+    iterator->index = 0;
+    iterator->kvm = iterator->context->tags[iterator->base].kvm;
+  }
+  return 1;
+}
+
+// Find a tag in a tag_set by key. Return true if found, false otherwise.
+static bool tag_set_get_tag(const struct tag_set *tags, const char *key,
+                            size_t key_len, census_tag *tag) {
+  char *kvp = tags->kvm;
+  for (int i = 0; i < tags->ntags; i++) {
+    struct raw_tag raw;
+    kvp = decode_tag(&raw, kvp, 0);
+    if (key_len == raw.key_len && memcmp(raw.key, key, key_len) == 0) {
+      tag->key = raw.key;
+      tag->value = raw.value;
+      tag->flags = raw.flags;
+      return true;
+    }
+  }
+  return false;
+}
+
+int census_context_get_tag(const census_context *context, const char *key,
+                           census_tag *tag) {
+  size_t key_len = strlen(key) + 1;
+  if (key_len == 1) {
+    return 0;
+  }
+  if (tag_set_get_tag(&context->tags[PROPAGATED_TAGS], key, key_len, tag) ||
+      tag_set_get_tag(&context->tags[LOCAL_TAGS], key, key_len, tag)) {
+    return 1;
+  }
+  return 0;
+}
+
+// Context encoding and decoding functions.
+//
+// Wire format for tag_set's on the wire:
+//
+// First, a tag set header:
+//
+// offset   bytes  description
+//   0        1    version number
+//   1        1    number of bytes in this header. This allows for future
+//                 expansion.
+//   2        1    number of bytes in each tag header.
+//   3        1    ntags value from tag set.
+//
+//   This is followed by the key/value memory from struct tag_set.
+
+#define ENCODED_VERSION 0      // Version number
+#define ENCODED_HEADER_SIZE 4  // size of tag set header
+
+// Encode a tag set. Returns 0 if buffer is too small.
+static size_t tag_set_encode(const struct tag_set *tags, char *buffer,
+                             size_t buf_size) {
+  if (buf_size < ENCODED_HEADER_SIZE + tags->kvm_used) {
+    return 0;
+  }
+  buf_size -= ENCODED_HEADER_SIZE;
+  *buffer++ = (char)ENCODED_VERSION;
+  *buffer++ = (char)ENCODED_HEADER_SIZE;
+  *buffer++ = (char)TAG_HEADER_SIZE;
+  *buffer++ = (char)tags->ntags;
+  if (tags->ntags == 0) {
+    return ENCODED_HEADER_SIZE;
+  }
+  memcpy(buffer, tags->kvm, tags->kvm_used);
+  return ENCODED_HEADER_SIZE + tags->kvm_used;
+}
+
+size_t census_context_encode(const census_context *context, char *buffer,
+                             size_t buf_size) {
+  return tag_set_encode(&context->tags[PROPAGATED_TAGS], buffer, buf_size);
+}
+
+// Decode a tag set.
+static void tag_set_decode(struct tag_set *tags, const char *buffer,
+                           size_t size) {
+  uint8_t version = (uint8_t)(*buffer++);
+  uint8_t header_size = (uint8_t)(*buffer++);
+  uint8_t tag_header_size = (uint8_t)(*buffer++);
+  tags->ntags = tags->ntags_alloc = (int)(*buffer++);
+  if (tags->ntags == 0) {
+    tags->ntags_alloc = 0;
+    tags->kvm_size = 0;
+    tags->kvm_used = 0;
+    tags->kvm = NULL;
+    return;
+  }
+  if (header_size != ENCODED_HEADER_SIZE) {
+    GPR_ASSERT(version != ENCODED_VERSION);
+    GPR_ASSERT(ENCODED_HEADER_SIZE < header_size);
+    buffer += (header_size - ENCODED_HEADER_SIZE);
+  }
+  tags->kvm_used = size - header_size;
+  tags->kvm_size = tags->kvm_used + CENSUS_MAX_TAG_KV_LEN;
+  tags->kvm = gpr_malloc(tags->kvm_size);
+  if (tag_header_size != TAG_HEADER_SIZE) {
+    // something new in the tag information. I don't understand it, so
+    // don't copy it over.
+    GPR_ASSERT(version != ENCODED_VERSION);
+    GPR_ASSERT(tag_header_size > TAG_HEADER_SIZE);
+    char *kvp = tags->kvm;
+    for (int i = 0; i < tags->ntags; i++) {
+      memcpy(kvp, buffer, TAG_HEADER_SIZE);
+      kvp += header_size;
+      struct raw_tag raw;
+      buffer =
+          decode_tag(&raw, (char *)buffer, tag_header_size - TAG_HEADER_SIZE);
+      memcpy(kvp, raw.key, (size_t)raw.key_len + raw.value_len);
+      kvp += raw.key_len + raw.value_len;
+    }
+  } else {
+    memcpy(tags->kvm, buffer, tags->kvm_used);
+  }
+}
+
+census_context *census_context_decode(const char *buffer, size_t size) {
+  census_context *context = gpr_malloc(sizeof(census_context));
+  memset(&context->tags[LOCAL_TAGS], 0, sizeof(struct tag_set));
+  if (buffer == NULL) {
+    memset(&context->tags[PROPAGATED_TAGS], 0, sizeof(struct tag_set));
+  } else {
+    tag_set_decode(&context->tags[PROPAGATED_TAGS], buffer, size);
+  }
+  memset(&context->status, 0, sizeof(context->status));
+  context->status.n_propagated_tags = context->tags[PROPAGATED_TAGS].ntags;
+  return context;
+}