Расчет контрольных сумм у файла - С/Си - C (СИ) - Ответ 9321259

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
 
enum
{
  no_error,
  error_file_open_fail,
  error_mem_alloc,
  error_file_read_error
};
 
struct TFileData
{
  uint32_t crc;
  uint32_t headerCrc;
  uint32_t remainderCrc;
};
 
uint32_t Crc32(const char* const buffer, const size_t bufferLength)
{
  uint32_t crc = 0;
  uint32_t remainder = 0;
 
  uint8_t octet = 0;
  
  static uint32_t lookupTable[256];
 
  static int isTableConstructed = 0;
 
  int i = 0;
  int j = 0;
 
  const char* bufferIterator = NULL;
  const char* bufferEndAddress = NULL;
 
  if (!isTableConstructed)
  {
    for (i = 0; i < 256; i++)
    {
      remainder = i;
      for (j = 0; j < 8; j++)
      {
        remainder = remainder >> 1;
 
        if (remainder & 1)
        {
          remainder = remainder ^ 0xEDB88320;
        }
      }
      lookupTable[i] = remainder;
    }
    isTableConstructed = 1;
  }
 
  crc = ~crc;
 
  bufferEndAddress = buffer + bufferLength;
  for (bufferIterator = buffer; bufferIterator < bufferEndAddress; bufferIterator++)
  {
    octet = *bufferIterator;
    crc = (crc >> 8) ^ lookupTable[(crc & 0xFF) ^ octet];
  }
 
  return ~crc;
}
 
int GetFileSize(const char* const fileName, size_t* const fileSizePtr)
{
  size_t fileSize = 0;
 
  FILE* f = fopen(fileName, "rb");
 
  if (f == NULL) return error_file_open_fail;
 
  fseek(f, 0, SEEK_END);
  fileSize = (size_t)ftell(f);
 
  fclose(f);
  *fileSizePtr = fileSize;
 
  return no_error;
}
 
int LoadFileToBuffer(const char* const fileName, char* const buffer, const size_t bufferLength)
{
  size_t bytesRead = 0;
 
  FILE* f = fopen(fileName, "rb");
 
  if (f == NULL) return error_file_open_fail;
 
  bytesRead = fread(buffer, 1, bufferLength, f);
  fclose(f);
 
  if (bytesRead != bufferLength) return error_file_read_error;
 
  return no_error;
}
 
void FillCrcData(const char* const buffer, const size_t bufferLength, struct TFileData* const crcDataPtr)
{
  crcDataPtr->crc           = Crc32(buffer, bufferLength);
  crcDataPtr->headerCrc     = Crc32(buffer, 48);
  crcDataPtr->remainderCrc  = Crc32(buffer + 48, bufferLength - 48);
}
 
void DisplayCrcData(struct TFileData* const crcDataPtr)
{
  printf("CRC data:\n"
    "total file CRC : %lX\n"
    "header CRC     : %lX\n"
    "remainder CRC  : %lX\n",
    crcDataPtr->crc,
    crcDataPtr->headerCrc,
    crcDataPtr->remainderCrc);
}
 
int ProcessFile(const char* const fileName, struct TFileData* const crcDataPtr)
{
  int errorCode = no_error;
 
  size_t fileSize = 0;
 
  char* buffer = NULL;
 
  errorCode = GetFileSize(fileName, &fileSize);
 
  if ((errorCode == no_error) && (fileSize > 0))
  {
    buffer = malloc(fileSize);
 
    if (buffer != NULL)
    {
      errorCode = LoadFileToBuffer(fileName, buffer, fileSize);
 
      if (errorCode == no_error) FillCrcData(buffer, fileSize, crcDataPtr);
    }
    else errorCode = error_mem_alloc;
  }
 
  return errorCode;
}
 
int main(void)
{
  struct TFileData fileData;
 
  ProcessFile("input.txt", &fileData);
 
  DisplayCrcData(&fileData);
 
  return 0;
}