/*
   * io_dp.c
   *
   * Implements the dynamic pointer interface.
   *
   * Based on GD.pm code by Lincoln Stein for interfacing to libgd.
   * Added support for reading as well as support for 'tell' and 'seek'.
   *
   * As will all I/O modules, most functions are for local use only (called
   * via function pointers in the I/O context).
   *
   * gdDPExtractData is the exception to this: it will return the pointer to
   * the internal data, and reset the internal storage.
   *
   * Written/Modified 1999, Philip Warner.
   *
 */

#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "gd.h"
#include "gdhelpers.h"

#define TRUE 1
#define FALSE 0

/* this is used for creating images in main memory */
typedef struct dpStruct
{
	void *data;
	int logicalSize;
	int realSize;
	int dataGood;
	int pos;
	int freeOK;
} dynamicPtr;

typedef struct dpIOCtx
{
	gdIOCtx ctx;
	dynamicPtr *dp;
} dpIOCtx;

typedef struct dpIOCtx *dpIOCtxPtr;

/* these functions operate on in-memory dynamic pointers */
static int allocDynamic (dynamicPtr * dp, int initialSize, void *data);
static int appendDynamic (dynamicPtr * dp, const void *src, int size);
static int gdReallocDynamic (dynamicPtr * dp, int required);
static int trimDynamic (dynamicPtr * dp);
static void gdFreeDynamicCtx (struct gdIOCtx *ctx);
static dynamicPtr *newDynamic (int initialSize, void *data, int freeOKFlag);

static int dynamicPutbuf (struct gdIOCtx *, const void *, int);
static void dynamicPutchar (struct gdIOCtx *, int a);

static int dynamicGetbuf (gdIOCtxPtr ctx, void *buf, int len);
static int dynamicGetchar (gdIOCtxPtr ctx);

static int dynamicSeek (struct gdIOCtx *, const int);
static long dynamicTell (struct gdIOCtx *);

/* return data as a dynamic pointer */
gdIOCtx * gdNewDynamicCtx (int initialSize, void *data)
{
	return gdNewDynamicCtxEx(initialSize, data, 1);
}

gdIOCtx * gdNewDynamicCtxEx (int initialSize, void *data, int freeOKFlag)
{
	dpIOCtx *ctx;
	dynamicPtr *dp;

	ctx = (dpIOCtx *) gdMalloc (sizeof (dpIOCtx));

	dp = newDynamic(initialSize, data, freeOKFlag);

	ctx->dp = dp;

	ctx->ctx.getC = dynamicGetchar;
	ctx->ctx.putC = dynamicPutchar;

	ctx->ctx.getBuf = dynamicGetbuf;
	ctx->ctx.putBuf = dynamicPutbuf;

	ctx->ctx.seek = dynamicSeek;
	ctx->ctx.tell = dynamicTell;

	ctx->ctx.gd_free = gdFreeDynamicCtx;

	return (gdIOCtx *) ctx;
}

void * gdDPExtractData (struct gdIOCtx *ctx, int *size)
{
	dynamicPtr *dp;
	dpIOCtx *dctx;
	void *data;

	dctx = (dpIOCtx *) ctx;
	dp = dctx->dp;

	/* clean up the data block and return it */
	if (dp->dataGood) {
		trimDynamic (dp);
		*size = dp->logicalSize;
		data = dp->data;
	} else {
		*size = 0;
		data = NULL;
		if (dp->data != NULL && dp->freeOK) {
			gdFree(dp->data);
		}
	}

	dp->data = NULL;
	dp->realSize = 0;
	dp->logicalSize = 0;

	return data;
}

static void gdFreeDynamicCtx (struct gdIOCtx *ctx)
{
	dynamicPtr *dp;
	dpIOCtx *dctx;

	dctx = (dpIOCtx *) ctx;
	dp = dctx->dp;

	gdFree(ctx);

	dp->realSize = 0;
	dp->logicalSize = 0;

	gdFree(dp);
}

static long dynamicTell (struct gdIOCtx *ctx)
{
	dpIOCtx *dctx;

	dctx = (dpIOCtx *) ctx;

	return (dctx->dp->pos);
}

static int dynamicSeek (struct gdIOCtx *ctx, const int pos)
{
	int bytesNeeded;
	dynamicPtr *dp;
	dpIOCtx *dctx;

	dctx = (dpIOCtx *) ctx;
	dp = dctx->dp;

	if (!dp->dataGood) {
		return FALSE;
	}

	bytesNeeded = pos;
	if (bytesNeeded > dp->realSize) {
		/* 2.0.21 */
		if (!dp->freeOK) {
			return FALSE;
		}
		gdReallocDynamic (dp, dp->realSize * 2);
	}

	/* if we get here, we can be sure that we have enough bytes to copy safely */

	/* Extend the logical size if we seek beyond EOF. */
	if (pos > dp->logicalSize) {
		dp->logicalSize = pos;
	}

	dp->pos = pos;

	return TRUE;
}

/* return data as a dynamic pointer */
static dynamicPtr * newDynamic (int initialSize, void *data, int freeOKFlag)
{
	dynamicPtr *dp;
	dp = (dynamicPtr *) gdMalloc (sizeof (dynamicPtr));

	allocDynamic (dp, initialSize, data);

	dp->pos = 0;
	dp->freeOK = freeOKFlag;

	return dp;
}

static int
dynamicPutbuf (struct gdIOCtx *ctx, const void *buf, int size)
{
  dpIOCtx *dctx;
  dctx = (dpIOCtx *) ctx;

  appendDynamic (dctx->dp, buf, size);

  if (dctx->dp->dataGood)
    {
      return size;
    }
  else
    {
      return -1;
    };

}

static void dynamicPutchar (struct gdIOCtx *ctx, int a)
{
	unsigned char b;
	dpIOCtxPtr dctx;

	b = a;
	dctx = (dpIOCtxPtr) ctx;

	appendDynamic(dctx->dp, &b, 1);
}

static int dynamicGetbuf (gdIOCtxPtr ctx, void *buf, int len)
{
	int rlen, remain;
	dpIOCtxPtr dctx;
	dynamicPtr *dp;

	dctx = (dpIOCtxPtr) ctx;
	dp = dctx->dp;

	remain = dp->logicalSize - dp->pos;
	if (remain >= len) {
		rlen = len;
	} else {
		if (remain == 0) {
			return EOF;
		}
		rlen = remain;
	}

	memcpy(buf, (void *) ((char *) dp->data + dp->pos), rlen);
	dp->pos += rlen;

	return rlen;
}

static int dynamicGetchar (gdIOCtxPtr ctx)
{
	unsigned char b;
	int rv;

	rv = dynamicGetbuf (ctx, &b, 1);
	if (rv != 1) {
		return EOF;
	} else {
		return b; 		/* (b & 0xff); */
	}
}

/* *********************************************************************

 * InitDynamic - Return a dynamically resizable void*
 *
 * *********************************************************************
 */
static int
allocDynamic (dynamicPtr * dp, int initialSize, void *data)
{

	if (data == NULL) {
		dp->logicalSize = 0;
		dp->dataGood = FALSE;
		dp->data = gdMalloc(initialSize);
	} else {
		dp->logicalSize = initialSize;
		dp->dataGood = TRUE;
		dp->data = data;
	}

	dp->realSize = initialSize;
	dp->dataGood = TRUE;
	dp->pos = 0;

	return TRUE;
}

/* append bytes to the end of a dynamic pointer */
static int appendDynamic (dynamicPtr * dp, const void *src, int size)
{
	int bytesNeeded;
	char *tmp;

	if (!dp->dataGood) {
		return FALSE;
	}

	/*  bytesNeeded = dp->logicalSize + size; */
	bytesNeeded = dp->pos + size;

	if (bytesNeeded > dp->realSize) {
		/* 2.0.21 */
		if (!dp->freeOK) {
			return FALSE;
		}
		gdReallocDynamic(dp, bytesNeeded * 2);
	}

	/* if we get here, we can be sure that we have enough bytes to copy safely */
	/*printf("Mem OK Size: %d, Pos: %d\n", dp->realSize, dp->pos); */

	tmp = (char *) dp->data;
	memcpy((void *) (tmp + (dp->pos)), src, size);
	dp->pos += size;

	if (dp->pos > dp->logicalSize) {
		dp->logicalSize = dp->pos;
	}

	return TRUE;
}

/* grow (or shrink) dynamic pointer */
static int gdReallocDynamic (dynamicPtr * dp, int required)
{
	void *newPtr;

	/* First try gdRealloc(). If that doesn't work, make a new memory block and copy. */
	if ((newPtr = gdRealloc(dp->data, required))) {
		dp->realSize = required;
		dp->data = newPtr;
		return TRUE;
	}

	/* create a new pointer */
	newPtr = gdMalloc(required);

	/* copy the old data into it */
	memcpy(newPtr, dp->data, dp->logicalSize);
	gdFree(dp->data);
	dp->data = newPtr;

	dp->realSize = required;

	return TRUE;
}

/* trim pointer so that its real and logical sizes match */
static int trimDynamic (dynamicPtr * dp)
{
	/* 2.0.21: we don't reallocate memory we don't own */
	if (!dp->freeOK) {
		return FALSE;
	}
	return gdReallocDynamic(dp, dp->logicalSize);
}