text: /*
   *
   * 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 <grpc/support/port_platform.h>
  
  #include <stdlib.h>
  #include <string.h>
  
  #include <grpc/grpc.h>
  #include <grpc/support/alloc.h>
  
  #include "src/core/lib/iomgr/error.h"
  #include "src/core/lib/slice/slice_internal.h"
  #include "src/core/lib/slice/slice_string_helpers.h"
  #include "src/core/lib/surface/validate_metadata.h"
  
  static grpc_error* conforms_to(grpc_slice slice, const uint8_t* legal_bits,
                                 const char* err_desc) {
    const uint8_t* p = GRPC_SLICE_START_PTR(slice);
    const uint8_t* e = GRPC_SLICE_END_PTR(slice);
    for (; p != e; p++) {
      int idx = *p;
      int byte = idx / 8;
      int bit = idx % 8;
      if ((legal_bits[byte] & (1 << bit)) == 0) {
        char* dump = grpc_dump_slice(slice, GPR_DUMP_HEX | GPR_DUMP_ASCII);
        grpc_error* error = grpc_error_set_str(
            grpc_error_set_int(GRPC_ERROR_CREATE_FROM_COPIED_STRING(err_desc),
                               GRPC_ERROR_INT_OFFSET,
                               p - GRPC_SLICE_START_PTR(slice)),
            GRPC_ERROR_STR_RAW_BYTES, grpc_slice_from_copied_string(dump));
        gpr_free(dump);
        return error;
      }
    }
    return GRPC_ERROR_NONE;
  }
  
  static int error2int(grpc_error* error) {
    int r = (error == GRPC_ERROR_NONE);
    GRPC_ERROR_UNREF(error);
    return r;
  }
  
  grpc_error* grpc_validate_header_key_is_legal(grpc_slice slice) {
    static const uint8_t legal_header_bits[256 / 8] = {
        0x00, 0x00, 0x00, 0x00, 0x00, 0x60, 0xff, 0x03, 0x00, 0x00, 0x00,
        0x80, 0xfe, 0xff, 0xff, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
    if (GRPC_SLICE_LENGTH(slice) == 0) {
      return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
          "Metadata keys cannot be zero length");
    }
    if (GRPC_SLICE_START_PTR(slice)[0] == ':') {
      return GRPC_ERROR_CREATE_FROM_STATIC_STRING(
          "Metadata keys cannot start with :");
    }
    return conforms_to(slice, legal_header_bits, "Illegal header key");
  }
  
  int grpc_header_key_is_legal(grpc_slice slice) {
    return error2int(grpc_validate_header_key_is_legal(slice));
  }
  
  grpc_error* grpc_validate_header_nonbin_value_is_legal(grpc_slice slice) {
    static const uint8_t legal_header_bits[256 / 8] = {
        0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
        0xff, 0xff, 0xff, 0xff, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
    return conforms_to(slice, legal_header_bits, "Illegal header value");
  }
  
  int grpc_header_nonbin_value_is_legal(grpc_slice slice) {
    return error2int(grpc_validate_header_nonbin_value_is_legal(slice));
  }
  
  int grpc_is_binary_header(grpc_slice slice) {
    if (GRPC_SLICE_LENGTH(slice) < 5) return 0;
    return 0 == memcmp(GRPC_SLICE_END_PTR(slice) - 4, "-bin", 4);
  }
  