text: /*
   *
   * Copyright 2015 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 <grpc/support/port_platform.h>
  
  #include "src/core/ext/transport/chttp2/transport/frame_goaway.h"
  
  #include <string.h>
  
  #include "absl/strings/str_format.h"
  
  #include <grpc/support/alloc.h>
  #include <grpc/support/log.h>
  
  #include "src/core/ext/transport/chttp2/transport/internal.h"
  
  void grpc_chttp2_goaway_parser_init(grpc_chttp2_goaway_parser* p) {
    p->debug_data = nullptr;
  }
  
  void grpc_chttp2_goaway_parser_destroy(grpc_chttp2_goaway_parser* p) {
    gpr_free(p->debug_data);
  }
  
  grpc_error_handle grpc_chttp2_goaway_parser_begin_frame(
      grpc_chttp2_goaway_parser* p, uint32_t length, uint8_t /*flags*/) {
    if (length < 8) {
      return GRPC_ERROR_CREATE_FROM_COPIED_STRING(
          absl::StrFormat("goaway frame too short (%d bytes)", length).c_str());
    }
  
    gpr_free(p->debug_data);
    p->debug_length = length - 8;
    p->debug_data = static_cast<char*>(gpr_malloc(p->debug_length));
    p->debug_pos = 0;
    p->state = GRPC_CHTTP2_GOAWAY_LSI0;
    return GRPC_ERROR_NONE;
  }
  
  grpc_error_handle grpc_chttp2_goaway_parser_parse(void* parser,
                                                    grpc_chttp2_transport* t,
                                                    grpc_chttp2_stream* /*s*/,
                                                    const grpc_slice& slice,
                                                    int is_last) {
    const uint8_t* const beg = GRPC_SLICE_START_PTR(slice);
    const uint8_t* const end = GRPC_SLICE_END_PTR(slice);
    const uint8_t* cur = beg;
    grpc_chttp2_goaway_parser* p =
        static_cast<grpc_chttp2_goaway_parser*>(parser);
  
    switch (p->state) {
      case GRPC_CHTTP2_GOAWAY_LSI0:
        if (cur == end) {
          p->state = GRPC_CHTTP2_GOAWAY_LSI0;
          return GRPC_ERROR_NONE;
        }
        p->last_stream_id = (static_cast<uint32_t>(*cur)) << 24;
        ++cur;
        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_GOAWAY_LSI1:
        if (cur == end) {
          p->state = GRPC_CHTTP2_GOAWAY_LSI1;
          return GRPC_ERROR_NONE;
        }
        p->last_stream_id |= (static_cast<uint32_t>(*cur)) << 16;
        ++cur;
        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_GOAWAY_LSI2:
        if (cur == end) {
          p->state = GRPC_CHTTP2_GOAWAY_LSI2;
          return GRPC_ERROR_NONE;
        }
        p->last_stream_id |= (static_cast<uint32_t>(*cur)) << 8;
        ++cur;
        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_GOAWAY_LSI3:
        if (cur == end) {
          p->state = GRPC_CHTTP2_GOAWAY_LSI3;
          return GRPC_ERROR_NONE;
        }
        p->last_stream_id |= (static_cast<uint32_t>(*cur));
        ++cur;
        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_GOAWAY_ERR0:
        if (cur == end) {
          p->state = GRPC_CHTTP2_GOAWAY_ERR0;
          return GRPC_ERROR_NONE;
        }
        p->error_code = (static_cast<uint32_t>(*cur)) << 24;
        ++cur;
        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_GOAWAY_ERR1:
        if (cur == end) {
          p->state = GRPC_CHTTP2_GOAWAY_ERR1;
          return GRPC_ERROR_NONE;
        }
        p->error_code |= (static_cast<uint32_t>(*cur)) << 16;
        ++cur;
        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_GOAWAY_ERR2:
        if (cur == end) {
          p->state = GRPC_CHTTP2_GOAWAY_ERR2;
          return GRPC_ERROR_NONE;
        }
        p->error_code |= (static_cast<uint32_t>(*cur)) << 8;
        ++cur;
        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_GOAWAY_ERR3:
        if (cur == end) {
          p->state = GRPC_CHTTP2_GOAWAY_ERR3;
          return GRPC_ERROR_NONE;
        }
        p->error_code |= (static_cast<uint32_t>(*cur));
        ++cur;
        ABSL_FALLTHROUGH_INTENDED;
      case GRPC_CHTTP2_GOAWAY_DEBUG:
        if (end != cur) {
          memcpy(p->debug_data + p->debug_pos, cur,
                 static_cast<size_t>(end - cur));
        }
        GPR_ASSERT((size_t)(end - cur) < UINT32_MAX - p->debug_pos);
        p->debug_pos += static_cast<uint32_t>(end - cur);
        p->state = GRPC_CHTTP2_GOAWAY_DEBUG;
        if (is_last) {
          grpc_chttp2_add_incoming_goaway(
              t, p->error_code, p->last_stream_id,
              grpc_slice_new(p->debug_data, p->debug_length, gpr_free));
          p->debug_data = nullptr;
        }
        return GRPC_ERROR_NONE;
    }
    GPR_UNREACHABLE_CODE(
        return GRPC_ERROR_CREATE_FROM_STATIC_STRING("Should never reach here"));
  }
  
  void grpc_chttp2_goaway_append(uint32_t last_stream_id, uint32_t error_code,
                                 const grpc_slice& debug_data,
                                 grpc_slice_buffer* slice_buffer) {
    grpc_slice header = GRPC_SLICE_MALLOC(9 + 4 + 4);
    uint8_t* p = GRPC_SLICE_START_PTR(header);
    uint32_t frame_length;
    GPR_ASSERT(GRPC_SLICE_LENGTH(debug_data) < UINT32_MAX - 4 - 4);
    frame_length = 4 + 4 + static_cast<uint32_t> GRPC_SLICE_LENGTH(debug_data);
  
    /* frame header: length */
    *p++ = static_cast<uint8_t>(frame_length >> 16);
    *p++ = static_cast<uint8_t>(frame_length >> 8);
    *p++ = static_cast<uint8_t>(frame_length);
    /* frame header: type */
    *p++ = GRPC_CHTTP2_FRAME_GOAWAY;
    /* frame header: flags */
    *p++ = 0;
    /* frame header: stream id */
    *p++ = 0;
    *p++ = 0;
    *p++ = 0;
    *p++ = 0;
    /* payload: last stream id */
    *p++ = static_cast<uint8_t>(last_stream_id >> 24);
    *p++ = static_cast<uint8_t>(last_stream_id >> 16);
    *p++ = static_cast<uint8_t>(last_stream_id >> 8);
    *p++ = static_cast<uint8_t>(last_stream_id);
    /* payload: error code */
    *p++ = static_cast<uint8_t>(error_code >> 24);
    *p++ = static_cast<uint8_t>(error_code >> 16);
    *p++ = static_cast<uint8_t>(error_code >> 8);
    *p++ = static_cast<uint8_t>(error_code);
    GPR_ASSERT(p == GRPC_SLICE_END_PTR(header));
    grpc_slice_buffer_add(slice_buffer, header);
    grpc_slice_buffer_add(slice_buffer, debug_data);
  }
  