mirror of
https://github.com/michaelrsweet/pdfio.git
synced 2025-08-29 15:22:06 +02:00
Safe work on streams - still need to implement predictors
This commit is contained in:
Michael R Sweet
249
pdfio-stream.c
249
pdfio-stream.c
@@ -14,6 +14,13 @@
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#include "pdfio-private.h"
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//
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// Local functions...
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//
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static ssize_t stream_read(pdfio_stream_t *st, char *buffer, size_t bytes);
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//
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// 'pdfioStreamClose()' - Close a (data) stream in a PDF file.
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//
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@@ -54,10 +61,35 @@ bool // O - `true` on success, `false` on EOF
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pdfioStreamConsume(pdfio_stream_t *st, // I - Stream
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size_t bytes)// I - Number of bytes to consume
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{
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// TODO: Implement me
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(void)st;
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(void)bytes;
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return (false);
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size_t remaining; // Remaining bytes in buffer
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ssize_t rbytes; // Bytes read
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// Range check input...
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if (!st || st->pdf->mode != _PDFIO_MODE_READ || !bytes)
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return (false);
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// Skip bytes in the stream buffer until we've consumed the requested number
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// or get to the end of the stream...
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while ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
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{
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bytes -= remaining;
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if ((rbytes = stream_read(st, st->buffer, sizeof(st->buffer))) > 0)
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{
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st->bufptr = st->buffer;
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st->bufend = st->buffer + rbytes;
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}
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else
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{
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st->bufptr = st->bufend = st->buffer;
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return (false);
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}
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}
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st->bufptr += bytes;
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return (true);
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}
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@@ -107,6 +139,9 @@ _pdfioStreamOpen(pdfio_obj_t *obj, // I - Object
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bool decode) // I - Decode/decompress the stream?
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{
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pdfio_stream_t *st; // Stream
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pdfio_dict_t *dict = pdfioObjGetDict(obj);
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// Object dictionary
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size_t length; // Length of stream
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// Allocate a new stream object...
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@@ -121,11 +156,36 @@ _pdfioStreamOpen(pdfio_obj_t *obj, // I - Object
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_pdfioFileSeek(st->pdf, obj->stream_offset, SEEK_SET);
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if ((length = (size_t)pdfioDictGetNumber(dict, "Length")) == 0)
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{
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// Length must be an indirect reference...
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pdfio_obj_t *lenobj; // Length object
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if ((lenobj = pdfioDictGetObject(dict, "Length")) == NULL)
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{
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_pdfioFileError(obj->pdf, "Unable to get length of stream.");
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free(st);
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return (NULL);
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}
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if (lenobj->value.type == PDFIO_VALTYPE_NONE)
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_pdfioObjLoad(lenobj);
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if (lenobj->value.type != PDFIO_VALTYPE_NUMBER || lenobj->value.value.number <= 0.0f)
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{
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_pdfioFileError(obj->pdf, "Unable to get length of stream.");
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free(st);
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return (NULL);
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}
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length = (size_t)lenobj->value.value.number;
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}
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st->remaining = length;
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if (decode)
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{
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// Try to decode/decompress the contents of this object...
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pdfio_dict_t *dict = pdfioObjGetDict(obj);
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// Object dictionary
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const char *filter = pdfioDictGetName(dict, "Filter");
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// Filter value
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@@ -146,6 +206,7 @@ _pdfioStreamOpen(pdfio_obj_t *obj, // I - Object
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else if (!strcmp(filter, "FlateDecode"))
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{
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// Flate compression
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#if 0 // TODO: Determine whether we need to implement support for predictors
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int bpc = (int)pdfioDictGetNumber(dict, "BitsPerComponent");
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// Bits per component
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int colors = (int)pdfioDictGetNumber(dict, "Colors");
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@@ -154,8 +215,26 @@ _pdfioStreamOpen(pdfio_obj_t *obj, // I - Object
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// Number of columns
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int predictor = (int)pdfioDictGetNumber(dict, "Predictor");
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// Predictory value, if any
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#endif // 0
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st->filter = PDFIO_FILTER_FLATE;
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st->flate.zalloc = (alloc_func)0;
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st->flate.zfree = (free_func)0;
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st->flate.opaque = (voidpf)0;
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st->flate.next_in = (Bytef *)st->cbuffer;
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st->flate.next_out = NULL;
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st->flate.avail_in = (uInt)_pdfioFileRead(st->pdf, st->cbuffer, sizeof(st->cbuffer));
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st->flate.avail_out = 0;
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if (inflateInit(&(st->flate)) != Z_OK)
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{
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_pdfioFileError(st->pdf, "Unable to start Flate filter.");
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free(st);
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return (NULL);
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}
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st->remaining -= st->flate.avail_in;
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}
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else if (!strcmp(filter, "LZWDecode"))
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{
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@@ -189,12 +268,40 @@ pdfioStreamPeek(pdfio_stream_t *st, // I - Stream
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void *buffer, // I - Buffer
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size_t bytes) // I - Size of buffer
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{
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// TODO: Implement me
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(void)st;
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(void)buffer;
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(void)bytes;
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size_t remaining; // Remaining bytes in buffer
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return (-1);
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// Range check input...
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if (!st || st->pdf->mode != _PDFIO_MODE_READ || !buffer || !bytes)
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return (-1);
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// See if we have enough bytes in the buffer...
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if ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
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{
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// No, shift the buffer and read more
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ssize_t rbytes; // Bytes read
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if (remaining > 0)
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memmove(st->buffer, st->bufptr, remaining);
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st->bufptr = st->buffer;
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st->bufend = st->buffer + remaining;
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if ((rbytes = stream_read(st, st->bufptr, sizeof(st->buffer) - remaining)) > 0)
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{
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st->bufend += rbytes;
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remaining += (size_t)rbytes;
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}
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}
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// Copy bytes from the buffer...
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if (bytes > remaining)
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bytes = remaining;
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memcpy(buffer, st->bufptr, bytes);
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// Return the number of bytes that were copied...
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return ((ssize_t)bytes);
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}
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@@ -247,12 +354,57 @@ pdfioStreamRead(
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void *buffer, // I - Buffer
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size_t bytes) // I - Bytes to read
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{
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// TODO: Implement me
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(void)st;
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(void)buffer;
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(void)bytes;
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char *bufptr = (char *)buffer;
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// Pointer into buffer
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size_t remaining; // Remaining bytes in buffer
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ssize_t rbytes; // Bytes read
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return (-1);
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// Range check input...
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if (!st || st->pdf->mode != _PDFIO_MODE_READ || !buffer || !bytes)
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return (-1);
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// Loop until we have the requested bytes or hit the end of the stream...
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while ((remaining = (size_t)(st->bufend - st->bufptr)) < bytes)
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{
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memcpy(bufptr, st->bufptr, remaining);
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bufptr += remaining;
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bytes -= remaining;
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if (bytes >= sizeof(st->buffer))
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{
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// Read large amounts directly to caller's buffer...
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if ((rbytes = stream_read(st, bufptr, bytes)) > 0)
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{
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bufptr += rbytes;
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bytes = 0;
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}
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st->bufptr = st->bufend = st->buffer;
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break;
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}
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else if ((rbytes = stream_read(st, st->buffer, sizeof(st->buffer))) > 0)
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{
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st->bufptr = st->buffer;
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st->bufend = st->buffer + rbytes;
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}
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else
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{
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st->bufptr = st->bufend = st->buffer;
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break;
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}
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}
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// Copy any remaining bytes from the stream buffer...
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if (bytes > 0)
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{
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memcpy(bufptr, st->bufptr, bytes);
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bufptr += bytes;
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st->bufptr += bytes;
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}
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// Return the number of bytes that were read...
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return (bufptr - (char *)buffer);
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}
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@@ -273,3 +425,68 @@ pdfioStreamWrite(
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return (false);
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}
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//
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// 'stream_read()' - Read data from a stream, including filters.
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//
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static ssize_t // O - Number of bytes read or `-1` on error
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stream_read(pdfio_stream_t *st, // I - Stream
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char *buffer, // I - Buffer
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size_t bytes) // I - Number of bytes to read
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{
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ssize_t rbytes; // Bytes read
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if (st->filter == PDFIO_FILTER_NONE)
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{
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// No filtering, but limit reads to the length of the stream...
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if (bytes > st->remaining)
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rbytes = _pdfioFileRead(st->pdf, buffer, st->remaining);
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else
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rbytes = _pdfioFileRead(st->pdf, buffer, bytes);
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if (rbytes > 0)
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st->remaining -= (size_t)rbytes;
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return (rbytes);
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}
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else if (st->filter == PDFIO_FILTER_FLATE)
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{
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// Deflate compression...
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int status; // Status of decompression
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if (st->flate.avail_in == 0)
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{
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// Read more from the file...
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if (sizeof(st->cbuffer) > st->remaining)
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rbytes = _pdfioFileRead(st->pdf, st->cbuffer, st->remaining);
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else
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rbytes = _pdfioFileRead(st->pdf, st->cbuffer, sizeof(st->cbuffer));
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if (rbytes <= 0)
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return (-1); // End of file...
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st->remaining -= (size_t)rbytes;
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st->flate.next_in = (Bytef *)st->cbuffer;
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st->flate.avail_in = (uInt)rbytes;
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}
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// Decompress into the buffer...
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st->flate.next_out = (Bytef *)buffer;
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st->flate.avail_out = (uInt)bytes;
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if ((status = inflate(&(st->flate), Z_NO_FLUSH)) < Z_OK)
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{
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_pdfioFileError(st->pdf, "Unable to decompress stream data: %d", status);
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return (-1);
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}
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return (st->flate.next_out - (Bytef *)buffer);
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}
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// If we get here something bad happened...
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return (-1);
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}
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