text: /*
   *
   * Copyright 2015, 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 "src/core/ext/transport/chttp2/transport/frame_window_update.h"
  #include "src/core/ext/transport/chttp2/transport/internal.h"
  
  #include <grpc/support/alloc.h>
  #include <grpc/support/log.h>
  #include <grpc/support/string_util.h>
  
  grpc_slice grpc_chttp2_window_update_create(
      uint32_t id, uint32_t window_update, grpc_transport_one_way_stats *stats) {
    static const size_t frame_size = 13;
    grpc_slice slice = grpc_slice_malloc(frame_size);
    stats->header_bytes += frame_size;
    uint8_t *p = GRPC_SLICE_START_PTR(slice);
  
    GPR_ASSERT(window_update);
  
    *p++ = 0;
    *p++ = 0;
    *p++ = 4;
    *p++ = GRPC_CHTTP2_FRAME_WINDOW_UPDATE;
    *p++ = 0;
    *p++ = (uint8_t)(id >> 24);
    *p++ = (uint8_t)(id >> 16);
    *p++ = (uint8_t)(id >> 8);
    *p++ = (uint8_t)(id);
    *p++ = (uint8_t)(window_update >> 24);
    *p++ = (uint8_t)(window_update >> 16);
    *p++ = (uint8_t)(window_update >> 8);
    *p++ = (uint8_t)(window_update);
  
    return slice;
  }
  
  grpc_error *grpc_chttp2_window_update_parser_begin_frame(
      grpc_chttp2_window_update_parser *parser, uint32_t length, uint8_t flags) {
    if (flags || length != 4) {
      char *msg;
      gpr_asprintf(&msg, "invalid window update: length=%d, flags=%02x", length,
                   flags);
      grpc_error *err = GRPC_ERROR_CREATE_FROM_COPIED_STRING(msg);
      gpr_free(msg);
      return err;
    }
    parser->byte = 0;
    parser->amount = 0;
    return GRPC_ERROR_NONE;
  }
  
  grpc_error *grpc_chttp2_window_update_parser_parse(
      grpc_exec_ctx *exec_ctx, void *parser, grpc_chttp2_transport *t,
      grpc_chttp2_stream *s, grpc_slice slice, int is_last) {
    uint8_t *const beg = GRPC_SLICE_START_PTR(slice);
    uint8_t *const end = GRPC_SLICE_END_PTR(slice);
    uint8_t *cur = beg;
    grpc_chttp2_window_update_parser *p = parser;
  
    while (p->byte != 4 && cur != end) {
      p->amount |= ((uint32_t)*cur) << (8 * (3 - p->byte));
      cur++;
      p->byte++;
    }
  
    if (s != NULL) {
      s->stats.incoming.framing_bytes += (uint32_t)(end - cur);
    }
  
    if (p->byte == 4) {
      uint32_t received_update = p->amount;
      if (received_update == 0 || (received_update & 0x80000000u)) {
        char *msg;
        gpr_asprintf(&msg, "invalid window update bytes: %d", p->amount);
        grpc_error *err = GRPC_ERROR_CREATE_FROM_COPIED_STRING(msg);
        gpr_free(msg);
        return err;
      }
      GPR_ASSERT(is_last);
  
      if (t->incoming_stream_id != 0) {
        if (s != NULL) {
          GRPC_CHTTP2_FLOW_CREDIT_STREAM("parse", t, s, outgoing_window_delta,
                                         received_update);
          if (grpc_chttp2_list_remove_stalled_by_stream(t, s)) {
            grpc_chttp2_become_writable(
                exec_ctx, t, s, GRPC_CHTTP2_STREAM_WRITE_INITIATE_UNCOVERED,
                "stream.read_flow_control");
          }
        }
      } else {
        bool was_zero = t->outgoing_window <= 0;
        GRPC_CHTTP2_FLOW_CREDIT_TRANSPORT("parse", t, outgoing_window,
                                          received_update);
        bool is_zero = t->outgoing_window <= 0;
        if (was_zero && !is_zero) {
          grpc_chttp2_initiate_write(exec_ctx, t, false,
                                     "new_global_flow_control");
        }
      }
    }
  
    return GRPC_ERROR_NONE;
  }
  