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pdfio-stream.c
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pdfio-stream.c
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//
// PDF stream functions for PDFio.
//
// Copyright © 2021-2024 by Michael R Sweet.
//
// Licensed under Apache License v2.0. See the file "LICENSE" for more
// information.
//
#include "pdfio-private.h"
//
// Local functions...
//
static unsigned char stream_paeth(unsigned char a, unsigned char b, unsigned char c);
static ssize_t stream_read(pdfio_stream_t *st, char *buffer, size_t bytes);
static bool stream_write(pdfio_stream_t *st, const void *buffer, size_t bytes);
static const char *zstrerror(int error);
//
// 'pdfioStreamClose()' - Close a (data) stream in a PDF file.
//
bool // O - `true` on success, `false` on failure
pdfioStreamClose(pdfio_stream_t *st) // I - Stream
{
bool ret = true; // Return value
// Range check input...
if (!st)
return (false);
// Finish reads/writes and free memory...
if (st->pdf->mode == _PDFIO_MODE_READ)
{
if (st->filter == PDFIO_FILTER_FLATE)
inflateEnd(&(st->flate));
}
else
{
// Close stream for writing...
if (st->filter == PDFIO_FILTER_FLATE)
{
// Finalize flate compression stream...
int status; // Deflate status
while ((status = deflate(&st->flate, Z_FINISH)) != Z_STREAM_END)
{
size_t bytes = sizeof(st->cbuffer) - st->flate.avail_out,
// Bytes to write
outbytes; // Actual bytes written
if (status < Z_OK && status != Z_BUF_ERROR)
{
_pdfioFileError(st->pdf, "Flate compression failed: %s", zstrerror(status));
ret = false;
goto done;
}
if (st->crypto_cb)
{
// Encrypt it first...
outbytes = (st->crypto_cb)(&st->crypto_ctx, st->cbuffer, st->cbuffer, bytes & (size_t)~15);
}
else
{
// No encryption
outbytes = bytes;
}
if (!_pdfioFileWrite(st->pdf, st->cbuffer, outbytes))
{
ret = false;
goto done;
}
if (bytes > outbytes)
{
bytes -= outbytes;
memmove(st->cbuffer, st->cbuffer + outbytes, bytes);
}
else
{
bytes = 0;
}
st->flate.next_out = (Bytef *)st->cbuffer + bytes;
st->flate.avail_out = (uInt)(sizeof(st->cbuffer) - bytes);
}
if (st->flate.avail_out < (uInt)sizeof(st->cbuffer))
{
// Write any residuals...
size_t bytes = sizeof(st->cbuffer) - st->flate.avail_out;
// Bytes to write
if (st->crypto_cb)
{
// Encrypt it first...
bytes = (st->crypto_cb)(&st->crypto_ctx, st->cbuffer, st->cbuffer, bytes);
}
if (!_pdfioFileWrite(st->pdf, st->cbuffer, bytes))
{
ret = false;
goto done;
}
}
deflateEnd(&st->flate);
}
else if (st->crypto_cb && st->bufptr > st->buffer)
{
// Encrypt and flush
uint8_t temp[8192]; // Temporary buffer
size_t outbytes; // Output bytes
outbytes = (st->crypto_cb)(&st->crypto_ctx, temp, (uint8_t *)st->buffer, (size_t)(st->bufptr - st->buffer));
if (!_pdfioFileWrite(st->pdf, temp, outbytes))
{
ret = false;
goto done;
}
}
// Save the length of this stream...
st->obj->stream_length = (size_t)(_pdfioFileTell(st->pdf) - st->obj->stream_offset);
// End of stream marker...
if (!_pdfioFilePuts(st->pdf, "\nendstream\nendobj\n"))
{
ret = false;
goto done;
}
// Update the length as needed...
if (st->length_obj)
{
st->length_obj->value.value.number = st->obj->stream_length;
pdfioObjClose(st->length_obj);
}
else if (st->obj->length_offset)
{
// Seek back to the "/Length 9999999999" we wrote...
if (_pdfioFileSeek(st->pdf, st->obj->length_offset, SEEK_SET) < 0)
{
ret = false;
goto done;
}
// Write the updated length value...
if (!_pdfioFilePrintf(st->pdf, "%-10lu", (unsigned long)st->obj->stream_length))
{
ret = false;
goto done;
}
// Seek to the end of the PDF file...
if (_pdfioFileSeek(st->pdf, 0, SEEK_END) < 0)
{
ret = false;
goto done;
}
}
}
done:
st->pdf->current_obj = NULL;
free(st->prbuffer);
free(st->psbuffer);
free(st);
return (ret);
}
//
// '_pdfioStreamCreate()' - Create a stream for writing.
//
// Note: pdfioObjCreateStream handles writing the object and its dictionary.
//
pdfio_stream_t * // O - Stream or `NULL` on error
_pdfioStreamCreate(
pdfio_obj_t *obj, // I - Object
pdfio_obj_t *length_obj, // I - Length object, if any
pdfio_filter_t compression) // I - Compression to apply
{
pdfio_stream_t *st; // Stream
// Allocate a new stream object...
if ((st = (pdfio_stream_t *)calloc(1, sizeof(pdfio_stream_t))) == NULL)
{
_pdfioFileError(obj->pdf, "Unable to allocate memory for a stream.");
return (NULL);
}
st->pdf = obj->pdf;
st->obj = obj;
st->length_obj = length_obj;
st->filter = compression;
st->bufptr = st->buffer;
st->bufend = st->buffer + sizeof(st->buffer);
if (obj->pdf->encryption)
{
uint8_t iv[64]; // Initialization vector
size_t ivlen = sizeof(iv); // Length of initialization vector, if any
if ((st->crypto_cb = _pdfioCryptoMakeWriter(st->pdf, obj, &st->crypto_ctx, iv, &ivlen)) == NULL)
{
// TODO: Add error message?
free(st);
return (NULL);
}
if (ivlen > 0)
_pdfioFileWrite(st->pdf, iv, ivlen);
}
if (compression == PDFIO_FILTER_FLATE)
{
// Flate compression
pdfio_dict_t *params = pdfioDictGetDict(obj->value.value.dict, "DecodeParms");
// Decoding parameters
int bpc = (int)pdfioDictGetNumber(params, "BitsPerComponent");
// Bits per component
int colors = (int)pdfioDictGetNumber(params, "Colors");
// Number of colors
int columns = (int)pdfioDictGetNumber(params, "Columns");
// Number of columns
int predictor = (int)pdfioDictGetNumber(params, "Predictor");
// Predictory value, if any
int status; // ZLIB status code
PDFIO_DEBUG("_pdfioStreamCreate: FlateDecode - BitsPerComponent=%d, Colors=%d, Columns=%d, Predictor=%d\n", bpc, colors, columns, predictor);
if (bpc == 0)
{
bpc = 8;
}
else if (bpc < 1 || bpc == 3 || (bpc > 4 && bpc < 8) || (bpc > 8 && bpc < 16) || bpc > 16)
{
_pdfioFileError(st->pdf, "Unsupported BitsPerColor value %d.", bpc);
free(st);
return (NULL);
}
if (colors == 0)
{
colors = 1;
}
else if (colors < 0 || colors > 4)
{
_pdfioFileError(st->pdf, "Unsupported Colors value %d.", colors);
free(st);
return (NULL);
}
if (columns == 0)
{
columns = 1;
}
else if (columns < 0)
{
_pdfioFileError(st->pdf, "Unsupported Columns value %d.", columns);
free(st);
return (NULL);
}
if ((predictor > 1 && predictor < 10) || predictor > 15)
{
_pdfioFileError(st->pdf, "Unsupported Predictor function %d.", predictor);
free(st);
return (NULL);
}
else if (predictor)
{
// Using a PNG predictor function
st->predictor = (_pdfio_predictor_t)predictor;
st->pbpixel = (size_t)(bpc * colors + 7) / 8;
st->pbsize = (size_t)(bpc * colors * columns + 7) / 8;
if (predictor >= 10)
st->pbsize ++; // Add PNG predictor byte
if ((st->prbuffer = calloc(1, st->pbsize - 1)) == NULL || (st->psbuffer = calloc(1, st->pbsize)) == NULL)
{
_pdfioFileError(st->pdf, "Unable to allocate %lu bytes for Predictor buffers.", (unsigned long)st->pbsize);
free(st->prbuffer);
free(st->psbuffer);
free(st);
return (NULL);
}
}
else
st->predictor = _PDFIO_PREDICTOR_NONE;
st->flate.next_out = (Bytef *)st->cbuffer;
st->flate.avail_out = (uInt)sizeof(st->cbuffer);
if ((status = deflateInit(&(st->flate), 9)) != Z_OK)
{
_pdfioFileError(st->pdf, "Unable to start Flate filter: %s", zstrerror(status));
free(st->prbuffer);
free(st->psbuffer);
free(st);
return (NULL);
}
}
return (st);
}
//
// 'pdfioStreamConsume()' - Consume bytes from the stream.
//
bool // O - `true` on success, `false` on EOF
pdfioStreamConsume(pdfio_stream_t *st, // I - Stream
size_t bytes)// I - Number of bytes to consume
{
size_t remaining; // Remaining bytes in buffer
ssize_t rbytes; // Bytes read
// Range check input...
if (!st || st->pdf->mode != _PDFIO_MODE_READ || !bytes)
return (false);
// Skip bytes in the stream buffer until we've consumed the requested number
// or get to the end of the stream...
while ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
{
bytes -= remaining;
if ((rbytes = stream_read(st, st->buffer, sizeof(st->buffer))) > 0)
{
st->bufptr = st->buffer;
st->bufend = st->buffer + rbytes;
}
else
{
st->bufptr = st->bufend = st->buffer;
return (false);
}
}
st->bufptr += bytes;
return (true);
}
//
// 'pdfioStreamGetToken()' - Read a single PDF token from a stream.
//
// This function reads a single PDF token from a stream. Operator tokens,
// boolean values, and numbers are returned as-is in the provided string buffer.
// String values start with the opening parenthesis ('(') but have all escaping
// resolved and the terminating parenthesis removed. Hexadecimal string values
// start with the opening angle bracket ('<') and have all whitespace and the
// terminating angle bracket removed.
//
bool // O - `true` on success, `false` on EOF
pdfioStreamGetToken(
pdfio_stream_t *st, // I - Stream
char *buffer, // I - String buffer
size_t bufsize) // I - Size of string buffer
{
_pdfio_token_t tb; // Token buffer/stack
bool ret; // Return value
// Range check input...
if (!st || st->pdf->mode != _PDFIO_MODE_READ || !buffer || !bufsize)
return (false);
// Read using the token engine...
_pdfioTokenInit(&tb, st->pdf, (_pdfio_tconsume_cb_t)pdfioStreamConsume, (_pdfio_tpeek_cb_t)pdfioStreamPeek, st);
ret = _pdfioTokenRead(&tb, buffer, bufsize);
_pdfioTokenFlush(&tb);
return (ret);
}
//
// '_pdfioStreamOpen()' - Create a stream for reading.
//
// Note: pdfioObjOpenStream handles loading the object's dictionary and
// getting the start of the stream data.
//
pdfio_stream_t * // O - Stream or `NULL` on error
_pdfioStreamOpen(pdfio_obj_t *obj, // I - Object
bool decode) // I - Decode/decompress the stream?
{
pdfio_stream_t *st; // Stream
pdfio_dict_t *dict = pdfioObjGetDict(obj);
// Object dictionary
const char *type; // Object type
PDFIO_DEBUG("_pdfioStreamOpen(obj=%p(%u), decode=%s)\n", obj, (unsigned)obj->number, decode ? "true" : "false");
// Allocate a new stream object...
if ((st = (pdfio_stream_t *)calloc(1, sizeof(pdfio_stream_t))) == NULL)
{
_pdfioFileError(obj->pdf, "Unable to allocate memory for a stream.");
return (NULL);
}
st->pdf = obj->pdf;
st->obj = obj;
if ((st->remaining = pdfioObjGetLength(obj)) == 0)
{
free(st);
return (NULL);
}
if (_pdfioFileSeek(st->pdf, obj->stream_offset, SEEK_SET) != obj->stream_offset)
{
free(st);
return (NULL);
}
type = pdfioObjGetType(obj);
if (obj->pdf->encryption && (!type || strcmp(type, "XRef")))
{
uint8_t iv[64]; // Initialization vector
size_t ivlen; // Length of initialization vector, if any
ivlen = (size_t)_pdfioFilePeek(st->pdf, iv, sizeof(iv));
if ((st->crypto_cb = _pdfioCryptoMakeReader(st->pdf, obj, &st->crypto_ctx, iv, &ivlen)) == NULL)
{
// TODO: Add error message?
free(st);
return (NULL);
}
PDFIO_DEBUG("_pdfioStreamOpen: ivlen=%d\n", (int)ivlen);
if (ivlen > 0)
_pdfioFileConsume(st->pdf, ivlen);
if (st->pdf->encryption >= PDFIO_ENCRYPTION_AES_128)
st->remaining = (st->remaining + 15) & (size_t)~15;
}
if (decode)
{
// Try to decode/decompress the contents of this object...
const char *filter = pdfioDictGetName(dict, "Filter");
// Filter value
pdfio_array_t *fa = pdfioDictGetArray(dict, "Filter");
// Filter array
if (!filter && fa && pdfioArrayGetSize(fa) == 1)
{
// Support single-valued arrays...
filter = pdfioArrayGetName(fa, 0);
}
if (!filter)
{
// No single filter name, do we have a compound filter?
if (fa)
{
// TODO: Implement compound filters...
_pdfioFileError(st->pdf, "Unsupported compound stream filter.");
free(st);
return (NULL);
}
// No filter, read as-is...
st->filter = PDFIO_FILTER_NONE;
}
else if (!strcmp(filter, "FlateDecode"))
{
// Flate compression
pdfio_dict_t *params = pdfioDictGetDict(dict, "DecodeParms");
// Decoding parameters
int bpc = (int)pdfioDictGetNumber(params, "BitsPerComponent");
// Bits per component
int colors = (int)pdfioDictGetNumber(params, "Colors");
// Number of colors
int columns = (int)pdfioDictGetNumber(params, "Columns");
// Number of columns
int predictor = (int)pdfioDictGetNumber(params, "Predictor");
// Predictory value, if any
int status; // ZLIB status
ssize_t rbytes; // Bytes read
PDFIO_DEBUG("_pdfioStreamOpen: FlateDecode - BitsPerComponent=%d, Colors=%d, Columns=%d, Predictor=%d\n", bpc, colors, columns, predictor);
st->filter = PDFIO_FILTER_FLATE;
if (bpc == 0)
{
bpc = 8;
}
else if (bpc < 1 || bpc == 3 || (bpc > 4 && bpc < 8) || (bpc > 8 && bpc < 16) || bpc > 16)
{
_pdfioFileError(st->pdf, "Unsupported BitsPerColor value %d.", bpc);
free(st);
return (NULL);
}
if (colors == 0)
{
colors = 1;
}
else if (colors < 0 || colors > 4)
{
_pdfioFileError(st->pdf, "Unsupported Colors value %d.", colors);
free(st);
return (NULL);
}
if (columns == 0)
{
columns = 1;
}
else if (columns < 0)
{
_pdfioFileError(st->pdf, "Unsupported Columns value %d.", columns);
free(st);
return (NULL);
}
if ((predictor > 2 && predictor < 10) || predictor > 15)
{
_pdfioFileError(st->pdf, "Unsupported Predictor function %d.", predictor);
free(st);
return (NULL);
}
else if (predictor > 1)
{
// Using a predictor function
st->predictor = (_pdfio_predictor_t)predictor;
st->pbpixel = (size_t)(bpc * colors + 7) / 8;
st->pbsize = (size_t)(bpc * colors * columns + 7) / 8;
if (predictor >= 10)
st->pbsize ++; // Add PNG predictor byte
if ((st->prbuffer = calloc(1, st->pbsize - 1)) == NULL || (st->psbuffer = calloc(1, st->pbsize)) == NULL)
{
_pdfioFileError(st->pdf, "Unable to allocate %lu bytes for Predictor buffers.", (unsigned long)st->pbsize);
free(st->prbuffer);
free(st->psbuffer);
free(st);
return (NULL);
}
}
else
st->predictor = _PDFIO_PREDICTOR_NONE;
PDFIO_DEBUG("_pdfioStreamOpen: pos=%ld\n", (long)_pdfioFileTell(st->pdf));
if (sizeof(st->cbuffer) > st->remaining)
rbytes = _pdfioFileRead(st->pdf, st->cbuffer, st->remaining);
else
rbytes = _pdfioFileRead(st->pdf, st->cbuffer, sizeof(st->cbuffer));
if (rbytes <= 0)
{
_pdfioFileError(st->pdf, "Unable to read bytes for stream.");
free(st->prbuffer);
free(st->psbuffer);
free(st);
return (NULL);
}
if (st->crypto_cb)
rbytes = (ssize_t)(st->crypto_cb)(&st->crypto_ctx, st->cbuffer, st->cbuffer, (size_t)rbytes);
st->flate.next_in = (Bytef *)st->cbuffer;
st->flate.avail_in = (uInt)rbytes;
PDFIO_DEBUG("_pdfioStreamOpen: avail_in=%u, cbuffer=<%02X%02X%02X%02X%02X%02X%02X%02X...>\n", st->flate.avail_in, st->cbuffer[0], st->cbuffer[1], st->cbuffer[2], st->cbuffer[3], st->cbuffer[4], st->cbuffer[5], st->cbuffer[6], st->cbuffer[7]);
if ((status = inflateInit(&(st->flate))) != Z_OK)
{
_pdfioFileError(st->pdf, "Unable to start Flate filter: %s", zstrerror(status));
free(st->prbuffer);
free(st->psbuffer);
free(st);
return (NULL);
}
st->remaining -= st->flate.avail_in;
}
else if (!strcmp(filter, "LZWDecode"))
{
// LZW compression
st->filter = PDFIO_FILTER_LZW;
}
else
{
// Something else we don't support
_pdfioFileError(st->pdf, "Unsupported stream filter '/%s'.", filter);
free(st);
return (NULL);
}
}
else
{
// Just return the stream data as-is...
st->filter = PDFIO_FILTER_NONE;
}
return (st);
}
//
// 'pdfioStreamPeek()' - Peek at data in a stream.
//
ssize_t // O - Bytes returned or `-1` on error
pdfioStreamPeek(pdfio_stream_t *st, // I - Stream
void *buffer, // I - Buffer
size_t bytes) // I - Size of buffer
{
size_t remaining; // Remaining bytes in buffer
// Range check input...
if (!st || st->pdf->mode != _PDFIO_MODE_READ || !buffer || !bytes)
return (-1);
// See if we have enough bytes in the buffer...
if ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
{
// No, shift the buffer and read more
ssize_t rbytes; // Bytes read
if (remaining > 0)
memmove(st->buffer, st->bufptr, remaining);
st->bufptr = st->buffer;
st->bufend = st->buffer + remaining;
if ((rbytes = stream_read(st, st->bufend, sizeof(st->buffer) - remaining)) > 0)
{
st->bufend += rbytes;
remaining += (size_t)rbytes;
}
}
// Copy bytes from the buffer...
if (bytes > remaining)
bytes = remaining;
memcpy(buffer, st->bufptr, bytes);
// Return the number of bytes that were copied...
return ((ssize_t)bytes);
}
//
// 'pdfioStreamPrintf()' - Write a formatted string to a stream.
//
bool // O - `true` on success, `false` on failure
pdfioStreamPrintf(
pdfio_stream_t *st, // I - Stream
const char *format, // I - `printf`-style format string
...) // I - Additional arguments as needed
{
char buffer[8192]; // String buffer
va_list ap; // Argument pointer
// Range check input...
if (!st || st->pdf->mode != _PDFIO_MODE_WRITE || !format)
return (false);
// Format the string...
va_start(ap, format);
_pdfio_vsnprintf(st->pdf, buffer, sizeof(buffer), format, ap);
va_end(ap);
// Write the string...
return (pdfioStreamWrite(st, buffer, strlen(buffer)));
}
//
// 'pdfioStreamPutChar()' - Write a single character to a stream.
//
bool // O - `true` on success, `false` on failure
pdfioStreamPutChar(pdfio_stream_t *st, // I - Stream
int ch) // I - Character
{
char buffer[1]; // Write buffer
if (!st || st->pdf->mode != _PDFIO_MODE_WRITE)
return (false);
buffer[0] = (char)ch;
return (pdfioStreamWrite(st, buffer, 1));
}
//
// 'pdfioStreamPuts()' - Write a literal string to a stream.
//
bool // O - `true` on success, `false` on failure
pdfioStreamPuts(pdfio_stream_t *st, // I - Stream
const char *s) // I - Literal string
{
if (!st || st->pdf->mode != _PDFIO_MODE_WRITE || !s)
return (false);
else
return (pdfioStreamWrite(st, s, strlen(s)));
}
//
// 'pdfioStreamRead()' - Read data from a stream.
//
// This function reads data from a stream. When reading decoded image data
// from a stream, you *must* read whole scanlines. The
// @link pdfioImageGetBytesPerLine@ function can be used to determine the
// proper read length.
//
ssize_t // O - Number of bytes read or `-1` on error
pdfioStreamRead(
pdfio_stream_t *st, // I - Stream
void *buffer, // I - Buffer
size_t bytes) // I - Bytes to read
{
char *bufptr = (char *)buffer;
// Pointer into buffer
size_t remaining; // Remaining bytes in buffer
ssize_t rbytes; // Bytes read
// Range check input...
if (!st || st->pdf->mode != _PDFIO_MODE_READ || !buffer || !bytes)
return (-1);
// Loop until we have the requested bytes or hit the end of the stream...
while ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
{
memcpy(bufptr, st->bufptr, remaining);
bufptr += remaining;
bytes -= remaining;
if (bytes >= sizeof(st->buffer))
{
// Read large amounts directly to caller's buffer...
if ((rbytes = stream_read(st, bufptr, bytes)) > 0)
bufptr += rbytes;
bytes = 0;
st->bufptr = st->bufend = st->buffer;
break;
}
else if ((rbytes = stream_read(st, st->buffer, sizeof(st->buffer))) > 0)
{
st->bufptr = st->buffer;
st->bufend = st->buffer + rbytes;
}
else
{
st->bufptr = st->bufend = st->buffer;
bytes = 0;
break;
}
}
// Copy any remaining bytes from the stream buffer...
if (bytes > 0)
{
memcpy(bufptr, st->bufptr, bytes);
bufptr += bytes;
st->bufptr += bytes;
}
// Return the number of bytes that were read...
return (bufptr - (char *)buffer);
}
//
// 'pdfioStreamWrite()' - Write data to a stream.
//
bool // O - `true` on success or `false` on failure
pdfioStreamWrite(
pdfio_stream_t *st, // I - Stream
const void *buffer, // I - Data to write
size_t bytes) // I - Number of bytes to write
{
size_t pbpixel, // Size of pixel in bytes
pbline, // Bytes per line
remaining; // Remaining bytes on this line
const unsigned char *bufptr, // Pointer into buffer
*bufsecond; // Pointer to second pixel in buffer
unsigned char *sptr, // Pointer into sbuffer
*pptr; // Previous raw buffer
PDFIO_DEBUG("pdfioStreamWrite(st=%p, buffer=%p, bytes=%lu)\n", st, buffer, (unsigned long)bytes);
// Range check input...
if (!st || st->pdf->mode != _PDFIO_MODE_WRITE || !buffer || !bytes)
return (false);
// Write it...
if (st->filter == PDFIO_FILTER_NONE)
{
// No filtering...
if (st->crypto_cb)
{
// Encrypt data before writing...
uint8_t temp[8192]; // Temporary buffer
size_t cbytes, // Current bytes
outbytes; // Output bytes
bufptr = (const unsigned char *)buffer;
while (bytes > 0)
{
if (st->bufptr > st->buffer || bytes < 16)
{
// Write through the stream's buffer...
if ((cbytes = bytes) > (size_t)(st->bufend - st->bufptr))
cbytes = (size_t)(st->bufend - st->bufptr);
memcpy(st->bufptr, bufptr, cbytes);
st->bufptr += cbytes;
if (st->bufptr >= st->bufend)
{
// Encrypt and flush
outbytes = (st->crypto_cb)(&st->crypto_ctx, temp, (uint8_t *)st->buffer, sizeof(st->buffer));
if (!_pdfioFileWrite(st->pdf, temp, outbytes))
return (false);
st->bufptr = st->buffer;
}
}
else
{
// Write directly up to sizeof(temp) bytes...
if ((cbytes = bytes) > sizeof(temp))
cbytes = sizeof(temp);
if (cbytes & 15)
{
// AES has a 16-byte block size, so save the last few bytes...
cbytes &= (size_t)~15;
}
outbytes = (st->crypto_cb)(&st->crypto_ctx, temp, bufptr, cbytes);
if (!_pdfioFileWrite(st->pdf, temp, outbytes))
return (false);
}
bytes -= cbytes;
bufptr += cbytes;
}
return (true);
}
else
{
// Write unencrypted...
return (_pdfioFileWrite(st->pdf, buffer, bytes));
}
}
pbline = st->pbsize - 1;
if (st->predictor == _PDFIO_PREDICTOR_NONE)
{
// No predictor, just write it out straight...
return (stream_write(st, buffer, bytes));
}
else if ((bytes % pbline) != 0)
{
_pdfioFileError(st->pdf, "Write buffer size must be a multiple of a complete row.");
return (false);
}
pbpixel = st->pbpixel;
bufptr = (const unsigned char *)buffer;
bufsecond = bufptr + pbpixel;
while (bytes > 0)
{
// Store the PNG predictor in the first byte of the buffer...
if (st->predictor == _PDFIO_PREDICTOR_PNG_AUTO)
st->psbuffer[0] = 4; // Use Paeth predictor for auto...
else
st->psbuffer[0] = (unsigned char)(st->predictor - 10);
// Then process the current line using the specified PNG predictor...
sptr = st->psbuffer + 1;
pptr = st->prbuffer;
switch (st->predictor)
{
default :
// Anti-compiler-warning code (NONE is handled above, TIFF is not supported for writing)
return (false);
case _PDFIO_PREDICTOR_PNG_NONE :
// No PNG predictor...
memcpy(sptr, buffer, pbline);
break;
case _PDFIO_PREDICTOR_PNG_SUB :
// Encode the difference from the previous column
for (remaining = pbline; remaining > 0; remaining --, bufptr ++, sptr ++)
{
if (bufptr >= bufsecond)
*sptr = *bufptr - bufptr[-(int)pbpixel];
else
*sptr = *bufptr;
}
break;
case _PDFIO_PREDICTOR_PNG_UP :
// Encode the difference from the previous line
for (remaining = pbline; remaining > 0; remaining --, bufptr ++, sptr ++, pptr ++)
{
*sptr = *bufptr - *pptr;
}
break;
case _PDFIO_PREDICTOR_PNG_AVERAGE :
// Encode the difference with the average of the previous column and line
for (remaining = pbline; remaining > 0; remaining --, bufptr ++, sptr ++, pptr ++)
{
if (bufptr >= bufsecond)
*sptr = *bufptr - (bufptr[-(int)pbpixel] + *pptr) / 2;
else
*sptr = *bufptr - *pptr / 2;
}
break;
case _PDFIO_PREDICTOR_PNG_PAETH :
case _PDFIO_PREDICTOR_PNG_AUTO :
// Encode the difference with a linear transform function
for (remaining = pbline; remaining > 0; remaining --, bufptr ++, sptr ++, pptr ++)
{
if (bufptr >= bufsecond)
*sptr = *bufptr - stream_paeth(bufptr[-(int)pbpixel], *pptr, pptr[-(int)pbpixel]);
else
*sptr = *bufptr - stream_paeth(0, *pptr, 0);
}
break;
}
// Write the encoded line...
if (!stream_write(st, st->psbuffer, st->pbsize))
return (false);
memcpy(st->prbuffer, buffer, pbline);
bytes -= pbline;
}
return (true);
}
//
// 'stream_paeth()' - PaethPredictor function for PNG decompression filter.
//
static unsigned char // O - Predictor value
stream_paeth(unsigned char a, // I - Left pixel
unsigned char b, // I - Top pixel
unsigned char c) // I - Top-left pixel
{
int p = a + b - c; // Initial estimate
int pa = abs(p - a); // Distance to a
int pb = abs(p - b); // Distance to b
int pc = abs(p - c); // Distance to c
return ((pa <= pb && pa <= pc) ? a : (pb <= pc) ? b : c);