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// buffer.cpp

#include "common.h"

// cross-platform facilities

#ifndef _WIN32

#define fopen_s(fp,filename,mode) *(fp) = fopen (filename, mode)

#endif // _WIN32

void Buffer_Initialize (buffer_t *buffer)

{

   // this function initializes a new buffer_t structure, resetting its data pointer and size.

   buffer->data = NULL; // allocate max_size bytes for data

   buffer->size = 0; // reset size

   return; // finished, buffer structure is empty

}

void Buffer_Forget (buffer_t *buffer)

{

   // this function forgets a buffer's contents, freeing its associated memory buffer,

   // and resets the buffer_t structure.

   if (buffer->data != NULL)

      free (buffer->data); // free buffer data

   buffer->data = NULL;

   buffer->size = 0; // reset data size

   return; // finished, buffer structure is virgin again

}

int Buffer_Append (buffer_t *buffer, char *data, unsigned long data_size)

{

   // this function appends the content of data to a buffer's data.

   // Returns 1 on success, 0 on error.

   char *new_data;

   // first, reallocate space to hold data_size bytes more

   new_data = (char *) realloc (buffer->data, buffer->size + data_size);

   if (new_data == NULL)

      return (0); // on failure, return an error value

   buffer->data = new_data; // save pointer to reallocated data

   memcpy (&buffer->data[buffer->size], data, data_size); // write new data at the end

   buffer->size += data_size; // and increment buffer size

   return (1); // buffer appended successfully, return SUCCESS

}

int Buffer_Prepend (buffer_t *buffer, char *data, unsigned long data_size)

{

   // this function prepends the content of data to a buffer's data.

   // Returns 1 on success, 0 on error.

   char *new_data;

   // first, reallocate space to hold data_size bytes more

   new_data = (char *) realloc (buffer->data, data_size + buffer->size);

   if (new_data == NULL)

      return (0); // on failure, return an error value

   buffer->data = new_data; // save pointer to reallocated data

   if (buffer->size > 0)

      memmove (&buffer->data[data_size], buffer->data, buffer->size); // move existing data to the end

   memcpy (buffer->data, data, data_size); // write new data at the beginning

   buffer->size += data_size; // and increment buffer size

   return (1); // buffer appended successfully, return SUCCESS

}

int Buffer_WriteAt (buffer_t *buffer, unsigned long write_index, char *data, unsigned long data_size)

{

   // this function writes the content of data to a buffer's data at position write_index.

   // Returns 1 on success, 0 on error.

   char *new_data;

   // see if we need to grow the data

   if (write_index + data_size > buffer->size)

   {

      // if so, reallocate data buffer at the right size

      new_data = (char *) realloc (buffer->data, write_index + data_size);

      if (new_data == NULL)

         return (0); // on failure, return an error value

      buffer->data = new_data; // save pointer to reallocated data

   }

   memcpy (&buffer->data[write_index], data, data_size); // write data in place

   if (write_index + data_size > buffer->size)

      buffer->size = write_index + data_size; // update data size only if it growed

   return (1); // buffer written successfully, return SUCCESS

}

int Buffer_ReadFromFile (buffer_t *buffer, const char *file_pathname)

{

   // this function copies the contents of file_pathname in a newly allocated data buffer

   // and fills in the buffer size accordingly. It is up to the caller to free that buffer.

   // Returns 1 on success, 0 on error.

   struct stat stat_buffer;

   FILE *fp;

   // start by reporting a zero length

   buffer->size = 0;

   // figure out file existence and size

   if (stat (file_pathname, &stat_buffer) != 0)

      return (0); // on failure, return an error value

   // allocate enough space for it

   if ((buffer->data = (char *) malloc (stat_buffer.st_size)) == NULL)

      return (0); // on failure, return an error value

   // open it for binary reading

   fopen_s (&fp, file_pathname, "rb");

   if (fp == NULL)

   {

      free (buffer->data);

      return (0); // on failure, return an error value

   }

   // and read it at once

   if (fread (buffer->data, 1, stat_buffer.st_size, fp) != (size_t) stat_buffer.st_size)

   {

      free (buffer->data);

      return (0); // on failure, return an error value

   }

   fclose (fp); // finished, close file

   buffer->size = stat_buffer.st_size; // report its size

   return (1); // and return SUCCESS

}

int Buffer_ReadFromFileW (buffer_t *buffer, const wchar_t *file_pathname)

{

   // this function copies the contents of file_pathname in a newly allocated data buffer

   // and fills in the buffer size accordingly. It is up to the caller to free that buffer.

   // Returns 1 on success, 0 on error.

   struct _stat stat_buffer;

   FILE *fp;

   // start by reporting a zero length

   buffer->size = 0;

   // figure out file existence and size

   if (_wstat (file_pathname, &stat_buffer) != 0)

      return (0); // on failure, return an error value

   // allocate enough space for it

   if ((buffer->data = (char *) malloc (stat_buffer.st_size)) == NULL)

      return (0); // on failure, return an error value

                  // open it for binary reading

   _wfopen_s (&fp, file_pathname, L"rb");

   if (fp == NULL)

   {

      free (buffer->data);

      return (0); // on failure, return an error value

   }

   // and read it at once

   if (fread (buffer->data, 1, stat_buffer.st_size, fp) != (size_t) stat_buffer.st_size)

   {

      free (buffer->data);

      return (0); // on failure, return an error value

   }

   fclose (fp); // finished, close file

   buffer->size = stat_buffer.st_size; // report its size

   return (1); // and return SUCCESS

}

int Buffer_WriteToFile (buffer_t *buffer, const char *file_pathname)

{

   // this function copies the contents of buffer's data into the file pointed to by

   // file_pathname. Returns 1 on success, 0 on error.

   FILE *fp;

   // open file for binary writing

   fopen_s (&fp, file_pathname, "wb");

   if (fp == NULL)

      return (0);

   // and write it at once

   if (fwrite (buffer->data, 1, buffer->size, fp) != (size_t) buffer->size)

      return (0);

   fclose (fp); // finished, close file

   return (1); // and return SUCCESS

}

int Buffer_WriteToFileW (buffer_t *buffer, const wchar_t *file_pathname)

{

   // this function copies the contents of buffer's data into the file pointed to by

   // file_pathname. Returns 1 on success, 0 on error.

   FILE *fp;

   // open file for binary writing

   _wfopen_s (&fp, file_pathname, L"wb");

   if (fp == NULL)

      return (0);

   // and write it at once

   if (fwrite (buffer->data, 1, buffer->size, fp) != (size_t) buffer->size)

      return (0);

   fclose (fp); // finished, close file

   return (1); // and return SUCCESS

}

char *Buffer_Find (buffer_t *buffer, char *needle, unsigned long needle_length)

{

   // returns a pointer to the first occurence of needle in buffer haystack, or NULL if not found

   unsigned long byte_index;

   if (buffer->size < needle_length)

      return (NULL); // consistency check: if buffer is too small for needle, return NULL

   // parse buffer from start to end

   for (byte_index = 0; byte_index < buffer->size - needle_length; byte_index++)

      if (memcmp (&buffer->data[byte_index], needle, needle_length) == 0)

         return (&buffer->data[byte_index]); // return the first match we find

   return (NULL); // definitely no needle in buffer

}

int Buffer_Compare (buffer_t *buffer1, buffer_t *buffer2)

{

   // compares two buffers and return 0 if they match, non-zero if they differ.

   // If their size differ, the difference between both is returned.

   // If their content differ, the result of memcmp() is returned.

   if (buffer1->size != buffer2->size)

      return (buffer2->size - buffer1->size); // buffers differ in size

   return (memcmp (buffer1->data, buffer2->data, buffer1->size)); // do a memcmp() on both buffers

}

unsigned long Buffer_OffsetOf (buffer_t *buffer, void *something)

{

   // returns the absolute offset of the data pointed to by something relatively to the beginning of buffer data

   return ((unsigned long) something - (unsigned long) buffer->data);

}