/*
* 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"

#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;
} 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 reallocDynamic (dynamicPtr* dp, int required);
static int trimDynamic (dynamicPtr* dp);
static void freeDynamicCtx(struct gdIOCtx* ctx);
static dynamicPtr* newDynamic(int initialSize, void *data);

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) {
  dpIOCtx 	*ctx;
  dynamicPtr* 	dp;

  ctx = (dpIOCtx*) malloc(sizeof(dpIOCtx));
  if (ctx == NULL) {
    return NULL;
  }

  dp = newDynamic(initialSize, data);
  if (!dp) {
    free(ctx);
    return NULL;
  };

  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.free = freeDynamicCtx;

  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) {
      free(dp->data);
    }
  }

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

  return data;
}

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

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

  free(ctx);

  /* clean up the data block and return it */
  if (dp->data != NULL) {
    free(dp->data);
    dp->data = NULL;
  }

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

  free(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) {
    if (!reallocDynamic(dp,dp->realSize*2)) {
      dp->dataGood = FALSE;
      return FALSE;
    }
  }

  /* 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) {
  dynamicPtr* dp;
  dp = (dynamicPtr*) malloc(sizeof(dynamicPtr));
  if (dp == NULL) {
    return NULL;
  }

  if (!allocDynamic(dp,initialSize, data))
    return NULL;

  dp->pos = 0;

  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 = malloc(initialSize);
  } else {
      dp->logicalSize = initialSize;
      dp->dataGood = TRUE;
      dp->data = data;
  }

  if (dp->data !=NULL) {
    dp->realSize = initialSize;
    dp->dataGood = TRUE;
    dp->pos = 0;
    return TRUE;
  } else {
    dp->realSize = 0;
    return FALSE;
  }
}

/* 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) {
    if (!reallocDynamic(dp,bytesNeeded*2)) {
      dp->dataGood = FALSE;
      return FALSE;
    }
  }

  /* 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
reallocDynamic (dynamicPtr* dp, int required) {
  void* newPtr;

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

  /* create a new pointer */
  newPtr = malloc(required);
  if (!newPtr) {
    dp->dataGood = FALSE;
    return FALSE;
  }

  /* copy the old data into it */
  memcpy(newPtr,dp->data,dp->logicalSize);
  free(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) {
  return reallocDynamic(dp,dp->logicalSize);
}

