gd_io_dp.c

下载来的一个看图软件的源代码

/*
   * 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;
  }
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);

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

  dp = newDynamic (initialSize, data);
  if (!dp)
    {
      gdFree (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 = 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)
	{
	  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);

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

  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)
    {
      if (!gdReallocDynamic (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 *) gdMalloc (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 = gdMalloc (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 (!gdReallocDynamic (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
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);
  if (!newPtr)
    {
      dp->dataGood = FALSE;
      return FALSE;
    }

  /* 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)
{
  return gdReallocDynamic (dp, dp->logicalSize);
}