/*
** buffer.c 
**
**	See function descriptions in buffer.h 
**	Written by Peter Sutton, May 2007.
*/

#include "buffer.h"
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

struct Buffer {
    char* data;		/* Bytes being stored. Memory is of size 'capacity' */
    int curPos;		/* Current reading position in buffer */
    int inUse;		/* Number of bytes stored in buffer (writing pos) */
    int capacity;	/* Size of the data array */
};

/* Function used internally to grow the buffer */
static void buf_grow(Buffer* buf, int requiredEmptySpace) 
{
    if(buf->inUse + requiredEmptySpace >= buf->capacity) {
	/* Buffer data space is not large enough to hold this - extend it */
	buf->capacity = buf->inUse + requiredEmptySpace + 1;
	buf->data = realloc(buf->data, buf->capacity);
    }
}

Buffer* buf_create(int initialSize)
{
    Buffer* buf;

    buf = (Buffer*)malloc(sizeof(Buffer));
    buf->data = malloc(initialSize);
    buf->curPos = 0;
    buf->inUse = 0;
    buf->capacity = initialSize;
    return buf;
}

void buf_append(Buffer* buf, char* data, int numBytes)
{
    buf_grow(buf, numBytes);
    memcpy(buf->data + buf->inUse, data, numBytes);
    buf->inUse += numBytes;
}

int buf_append_from_fd(Buffer* buf, int fd, int maxBytes)
{
    int numBytesRead;
    buf_grow(buf, maxBytes);
    numBytesRead = read(fd, buf->data + buf->inUse, maxBytes);
    if(numBytesRead > 0) {
	buf->inUse += numBytesRead;
    }
    return numBytesRead;
}

char* buf_get_data(Buffer* buf)
{
    /* Null terminate the buffer */
    buf->data[buf->inUse] = '\0';
    return buf->data + buf->curPos;
}

void buf_delete(Buffer* buf)
{
    if(buf) {
	free(buf->data);
	free(buf);
    }
}

int buf_num_bytes_stored(Buffer* buf)
{
    return (buf->inUse - buf->curPos);
}

void buf_consume(Buffer* buf, int bytesConsumed)
{
    buf->curPos += bytesConsumed;
    if(buf->curPos == buf->inUse) {
	/* Complete buffer has been read - reset buffer */
	buf->curPos = 0;
	buf->inUse = 0;
    }
}

char* buf_extract_line(Buffer* buf)
{
    int pos;
    char* returnValue;

    pos = buf->curPos;
    while(pos < buf->inUse && buf->data[pos] != '\n') {
	pos++;
    }
    if(buf->data[pos] != '\n') {
	/* Reached end of buffer without finding newline */
	return NULL;
    }
    /* Have found newline - replace it by a null (along with any preceding \r)
    */
    buf->data[pos] = '\0';
    if(pos > buf->curPos && buf->data[pos-1] =='\r') {
	buf->data[pos-1] = '\0';
    }

    /* Consume the data */
    returnValue = buf->data + buf->curPos;
    buf->curPos = pos + 1;
    return returnValue;
}