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buffer.c
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buffer.c
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//
// Copyright(C) 2017 Alex Mayfield
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// DESCRIPTION:
// A simple buffer and reader implementation.
//
#ifdef _WIN32
#include "buffer.h"
#include <stdlib.h>
//
// Create a new buffer.
//
buffer_t *NewBuffer()
{
buffer_t *buf = malloc(sizeof(buffer_t));
buf->buffer_end = buf->buffer + BUFFER_SIZE;
Buffer_Clear(buf);
return buf;
}
//
// Free a buffer.
//
void DeleteBuffer(buffer_t *buf)
{
free(buf);
}
//
// Return the data in the buffer.
//
int Buffer_Data(buffer_t *buf, byte **data)
{
*data = buf->data;
return buf->data_len;
}
//
// Push data onto the end of the buffer.
//
boolean Buffer_Push(buffer_t *buf, const void *data, int len)
{
ptrdiff_t space_begin, space_end;
if (len <= 0)
{
// Do nothing, successfully.
return true;
}
space_begin = buf->data - buf->buffer;
space_end = buf->buffer_end - buf->data_end;
if (len > space_end)
{
if (len > space_begin + space_end)
{
// Don't overflow the buffer.
return false;
}
// Move our data to the front of the buffer.
memmove(buf->buffer, buf->data, buf->data_len);
buf->data = buf->buffer;
buf->data_end = buf->buffer + buf->data_len;
}
// Append to the buffer.
memcpy(buf->data_end, data, len);
buf->data_len += len;
buf->data_end = buf->data + buf->data_len;
return true;
}
//
// Shift len bytes off of the front of the buffer.
//
void Buffer_Shift(buffer_t *buf, int len)
{
ptrdiff_t max_shift;
if (len <= 0)
{
// Do nothing.
return;
}
max_shift = buf->data_end - buf->data;
if (len >= max_shift)
{
// If the operation would clear the buffer, just zero everything.
Buffer_Clear(buf);
}
else
{
buf->data += len;
buf->data_len -= len;
}
}
//
// Clear the buffer.
//
void Buffer_Clear(buffer_t *buf)
{
buf->data = buf->buffer;
buf->data_end = buf->buffer;
buf->data_len = 0;
}
//
// Create a new buffer reader.
//
// WARNING: This reader will invalidate if the underlying buffer changes.
// Use it, then delete it before you touch the underlying buffer again.
//
buffer_reader_t *NewReader(buffer_t* buffer)
{
buffer_reader_t *reader = malloc(sizeof(buffer_reader_t));
reader->buffer = buffer;
reader->pos = buffer->data;
return reader;
}
//
// Delete a buffer reader.
//
void DeleteReader(buffer_reader_t *reader)
{
free(reader);
}
//
// Count the number of bytes read thus far.
//
int Reader_BytesRead(buffer_reader_t *reader)
{
return reader->pos - reader->buffer->data;
}
//
// Read an unsigned byte from a buffer.
//
boolean Reader_ReadInt8(buffer_reader_t *reader, uint8_t *out)
{
byte *data, *data_end;
int len = Buffer_Data(reader->buffer, &data);
data_end = data + len;
if (data_end - reader->pos < 1)
{
return false;
}
*out = (uint8_t)*reader->pos;
reader->pos += 1;
return true;
}
//
// Read an unsigned short from a buffer.
//
boolean Reader_ReadInt16(buffer_reader_t *reader, uint16_t *out)
{
byte *data, *data_end, *dp;
int len = Buffer_Data(reader->buffer, &data);
data_end = data + len;
dp = reader->pos;
if (data_end - reader->pos < 2)
{
return false;
}
*out = (uint16_t)((dp[0] << 8) | dp[1]);
reader->pos += 2;
return true;
}
//
// Read an unsigned int from a buffer.
//
boolean Reader_ReadInt32(buffer_reader_t *reader, uint32_t *out)
{
byte *data, *data_end, *dp;
int len = Buffer_Data(reader->buffer, &data);
data_end = data + len;
dp = reader->pos;
if (data_end - reader->pos < 4)
{
return false;
}
*out = (uint32_t)((dp[0] << 24) | (dp[1] << 16) | (dp[2] << 8) | dp[3]);
reader->pos += 4;
return true;
}
//
// Read a string from a buffer.
//
char *Reader_ReadString(buffer_reader_t *reader)
{
byte *data, *data_start, *data_end, *dp;
int len = Buffer_Data(reader->buffer, &data);
data_start = reader->pos;
data_end = data + len;
dp = reader->pos;
while (dp < data_end && *dp != '\0')
{
dp++;
}
if (dp >= data_end)
{
// Didn't see a null terminator, not a complete string.
return NULL;
}
reader->pos = dp + 1;
return (char*)data_start;
}
#endif // #ifdef _WIN32