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Safe work on streams - still need to implement predictors

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Michael R Sweet
2021-05-07 08:47:49 -04:00
parent c61d6ad686
commit 44325ce2d9
5 changed files with 355 additions and 24 deletions
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89
pdfio-file.c
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@@ -537,14 +537,19 @@ load_xref(pdfio_file_t *pdf, // I - PDF file
return (false);
}
PDFIO_DEBUG("load_xref: xref_offset=%lu, line='%s'\n", (unsigned long)xref_offset, line);
if (isdigit(line[0] & 255) && strlen(line) > 4 && !strcmp(line + strlen(line) - 4, " obj"))
{
// Cross-reference stream
pdfio_obj_t *obj; // Object
size_t i; // Looping var
pdfio_array_t *w_array; // W array
size_t w[3]; // Size of each cross-reference field
size_t w_2, // Offset to second field
w_3; // Offset to third field
size_t w_total; // Total length
pdfio_stream_t *st; // Stream with
pdfio_stream_t *st; // Stream
unsigned char buffer[32]; // Read buffer
if ((number = strtoimax(line, &ptr, 10)) < 1)
@@ -568,6 +573,8 @@ load_xref(pdfio_file_t *pdf, // I - PDF file
return (false);
}
PDFIO_DEBUG("load_xref: Loading object %lu %u.\n", (unsigned long)number, (unsigned)generation);
if ((obj = add_obj(pdf, (size_t)number, (unsigned short)generation, xref_offset)) == NULL)
{
_pdfioFileError(pdf, "Unable to allocate memory for object.");
@@ -587,7 +594,85 @@ load_xref(pdfio_file_t *pdf, // I - PDF file
obj->value = trailer;
// TODO: read stream
if (!_pdfioFileGetToken(pdf, line, sizeof(line)) || strcmp(line, "stream"))
{
_pdfioFileError(pdf, "Unable to get stream after xref dictionary.");
return (false);
}
obj->stream_offset = _pdfioFileTell(pdf);
if ((w_array = pdfioDictGetArray(trailer.value.dict, "W")) == NULL)
{
_pdfioFileError(pdf, "Cross-reference stream does not have required W key.");
return (false);
}
w[0] = (size_t)pdfioArrayGetNumber(w_array, 0);
w[1] = (size_t)pdfioArrayGetNumber(w_array, 1);
w[2] = (size_t)pdfioArrayGetNumber(w_array, 2);
w_total = w[0] + w[1] + w[2];
w_2 = w[0];
w_3 = w[0] + w[1];
if (w[1] == 0 || w[2] > 2 || w_total > sizeof(buffer))
{
_pdfioFileError(pdf, "Cross-reference stream has invalid W key.");
return (false);
}
if ((st = pdfioObjOpenStream(obj, true)) == NULL)
{
_pdfioFileError(pdf, "Unable to open cross-reference stream.");
return (false);
}
while (pdfioStreamRead(st, buffer, w_total) > 0)
{
PDFIO_DEBUG("load_xref: %02X%02X%02X%02X%02X\n", buffer[0], buffer[1], buffer[2], buffer[3], buffer[4]);
// Check whether this is an object definition...
if (w[0] > 0)
{
if (buffer[0] == 0)
{
// Ignore free objects...
continue;
}
else if (buffer[0] == 2)
{
// TODO: Add support for compressed object streams...
// Compressed object...
_pdfioFileError(pdf, "PDF file contains compressed object streams which are not currently supported.");
continue;
}
}
for (i = 1, offset = buffer[w_2]; i < w[1]; i ++)
offset = (offset << 8) | buffer[w_2 + i];
switch (w[2])
{
default :
generation = 0;
break;
case 1 :
generation = buffer[w_3];
break;
case 2 :
generation = (buffer[w_3] << 8) | buffer[w_3 + 1];
break;
}
// Create a placeholder for the object in memory...
if (pdfioFileFindObject(pdf, (size_t)number))
continue; // Don't replace newer object...
if (!add_obj(pdf, (size_t)number, (unsigned short)generation, offset))
return (false);
}
pdfioStreamClose(st);
}
else if (!strcmp(line, "xref"))
{