text: // Copyright 2021 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/lib/slice/slice_split.h"
  
  #include <string.h>
  
  #include <grpc/support/log.h>
  
  /** Finds the initial (\a begin) and final (\a end) offsets of the next
   * substring from \a str + \a read_offset until the next \a sep or the end of \a
   * str.
   *
   * Returns 1 and updates \a begin and \a end. Returns 0 otherwise. */
  static int slice_find_separator_offset(const grpc_slice str, const char* sep,
                                         const size_t read_offset, size_t* begin,
                                         size_t* end) {
    size_t i;
    const uint8_t* str_ptr = GRPC_SLICE_START_PTR(str) + read_offset;
    const size_t str_len = GRPC_SLICE_LENGTH(str) - read_offset;
    const size_t sep_len = strlen(sep);
    if (str_len < sep_len) {
      return 0;
    }
  
    for (i = 0; i <= str_len - sep_len; i++) {
      if (memcmp(str_ptr + i, sep, sep_len) == 0) {
        *begin = read_offset;
        *end = read_offset + i;
        return 1;
      }
    }
    return 0;
  }
  
  static void skip_leading_trailing_spaces(const uint8_t* str_buffer,
                                           size_t* begin, size_t* end) {
    while (*begin < *end && str_buffer[*begin] == ' ') {
      (*begin)++;
    }
    while (*begin < *end && str_buffer[*end - 1] == ' ') {
      (*end)--;
    }
  }
  
  static void grpc_slice_split_inner(grpc_slice str, const char* sep,
                                     grpc_slice_buffer* dst, bool no_space) {
    const size_t sep_len = strlen(sep);
    size_t begin, end;
    const uint8_t* str_buffer = GRPC_SLICE_START_PTR(str);
    size_t sep_pos;
  
    GPR_ASSERT(sep_len > 0);
  
    if (slice_find_separator_offset(str, sep, 0, &begin, &end) != 0) {
      do {
        sep_pos = end;
        if (no_space) {
          skip_leading_trailing_spaces(str_buffer, &begin, &end);
        }
        grpc_slice_buffer_add_indexed(dst, grpc_slice_sub(str, begin, end));
      } while (slice_find_separator_offset(str, sep, sep_pos + sep_len, &begin,
                                           &end) != 0);
      begin = sep_pos + sep_len;
      end = GRPC_SLICE_LENGTH(str);
      if (no_space) {
        skip_leading_trailing_spaces(str_buffer, &begin, &end);
      }
      grpc_slice_buffer_add_indexed(dst, grpc_slice_sub(str, begin, end));
    } else { /* no sep found, add whole input */
      begin = 0;
      end = GRPC_SLICE_LENGTH(str);
      if (no_space) {
        skip_leading_trailing_spaces(str_buffer, &begin, &end);
      }
      grpc_slice_buffer_add_indexed(dst, grpc_slice_sub(str, begin, end));
    }
  }
  
  void grpc_slice_split(grpc_slice str, const char* sep, grpc_slice_buffer* dst) {
    grpc_slice_split_inner(str, sep, dst, false);
  }
  
  void grpc_slice_split_without_space(grpc_slice str, const char* sep,
                                      grpc_slice_buffer* dst) {
    grpc_slice_split_inner(str, sep, dst, true);
  }
  