gd_io_ss.c

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/*
   * io_ss.c
   *
   * Implements the Source/Sink interface.
   *
   * As will all I/O modules, most functions are for local use only (called
   * via function pointers in the I/O context).
   *
   * The Source/Sink model is the primary 'user' interface for alternate data
   * sources; the IOCtx interface is intended (at least in version 1.5) to be
   * used internally until it settles down a bit.
   *
   * This module just layers the Source/Sink interface on top of the IOCtx; no
   * support is provided for tell/seek, so GD2 writing is not possible, and
   * retrieving parts of GD2 files is also not possible.
   *
   * A new SS context does not need to be created with both a Source and a Sink.
   *
   * Written/Modified 1999, Philip Warner.
   *
 */
 
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "gd.h"
#include "gdhelpers.h"
 
/* this is used for creating images in main memory */
 
typedef struct ssIOCtx
{
    gdIOCtx ctx;
    gdSourcePtr src;
    gdSinkPtr snk;
} ssIOCtx;
 
typedef struct ssIOCtx *ssIOCtxPtr;
 
gdIOCtx *gdNewSSCtx (gdSourcePtr src, gdSinkPtr snk);
 
static int sourceGetbuf (gdIOCtx *, void *, int);
static int sourceGetchar (gdIOCtx * ctx);
static int sinkPutbuf (gdIOCtx * ctx, const void *buf, int size);
static void sinkPutchar (gdIOCtx * ctx, int a);
static void gdFreeSsCtx (gdIOCtx * ctx);
 
/* return data as a dynamic pointer */
gdIOCtx * gdNewSSCtx (gdSourcePtr src, gdSinkPtr snk)
{
    ssIOCtxPtr ctx;
 
    ctx = (ssIOCtxPtr) gdMalloc (sizeof (ssIOCtx));
 
    ctx->src = src;
    ctx->snk = snk;
 
    ctx->ctx.getC = sourceGetchar;
    ctx->ctx.getBuf = sourceGetbuf;
 
    ctx->ctx.putC = sinkPutchar;
    ctx->ctx.putBuf = sinkPutbuf;
 
    ctx->ctx.tell = NULL;
    ctx->ctx.seek = NULL;
 
    ctx->ctx.gd_free = gdFreeSsCtx;
 
    return (gdIOCtx *) ctx;
}
 
static void gdFreeSsCtx (gdIOCtx * ctx)
{
    gdFree(ctx);
}
 
 
static int sourceGetbuf (gdIOCtx * ctx, void *buf, int size)
{
    ssIOCtx *lctx;
    int res;
 
    lctx = (ssIOCtx *) ctx;
 
    res = ((lctx->src->source) (lctx->src->context, buf, size));
 
    /*
     * Translate the return values from the Source object:
     * 0 is EOF, -1 is error
     */
 
    if (res == 0) {
        return EOF;
    } else if (res < 0) {
        return 0;
    } else {
        return res;
    }
}
 
static int sourceGetchar (gdIOCtx * ctx)
{
    int res;
    unsigned char buf;
 
    res = sourceGetbuf (ctx, &buf, 1);
 
    if (res == 1) {
        return buf;
    } else {
        return EOF;
    }
}
 
static int sinkPutbuf (gdIOCtx * ctx, const void *buf, int size)
{
    ssIOCtxPtr lctx;
    int res;
 
    lctx = (ssIOCtx *) ctx;
 
    res = (lctx->snk->sink) (lctx->snk->context, buf, size);
 
    if (res <= 0) {
        return 0;
    } else {
        return res;
    }
}
 
static void sinkPutchar (gdIOCtx * ctx, int a)
{
    unsigned char b;
 
    b = a;
    sinkPutbuf (ctx, &b, 1);
}