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Add xref stream support (Issue #10)
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@michaelrsweet
michaelrsweet committed Feb 16, 2025
1 parent 8d72f22 commit aeee24b
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Showing 2 changed files with 192 additions and 35 deletions.
2 changes: 2 additions & 0 deletions CHANGES.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@ v1.5.0 - YYYY-MM-DD

- Added support for embedded color profiles in JPEG images (Issue #7)
- Added `pdfioFileCreateICCObjFromData` API.
- Added support for writing cross-reference streams for PDF 1.5 and newer files
(Issue #10)
- Added `pdfioFileGetModDate()` API (Issue #88)
- Added support for using libpng to embed PNG images in PDF output (Issue #90)
- Now support opening damaged PDF files (Issue #45)
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225 changes: 190 additions & 35 deletions pdfio-file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2358,59 +2358,214 @@ write_trailer(pdfio_file_t *pdf) // I - PDF file
bool ret = true; // Return value
off_t xref_offset; // Offset to xref table
size_t i; // Looping var
pdfio_obj_t *obj; // Current object


// Write the xref table...
// TODO: Look at adding support for xref streams...
xref_offset = _pdfioFileTell(pdf);

if (!_pdfioFilePrintf(pdf, "xref\n0 %lu \n0000000000 65535 f \n", (unsigned long)pdf->num_objs + 1))
// TODO: Figure out how to do xref streams with encrypted output
if (strcmp(pdf->version, "1.5") >= 0 && !pdf->output_cb && !pdf->encrypt_obj)
{
_pdfioFileError(pdf, "Unable to write cross-reference table.");
ret = false;
goto done;
}
// Write a cross-reference stream...
pdfio_dict_t *xref_dict; // Object dictionary
pdfio_array_t *w_array; // W array
pdfio_obj_t *xref_obj; // Object
pdfio_stream_t *xref_st; // Stream
int offsize; // Size of object offsets
unsigned char buffer[10]; // Buffer entry

// Figure out how many bytes are needed for the object numbers
if (xref_offset < 0xff)
offsize = 1;
else if (xref_offset < 0xffff)
offsize = 2;
else if (xref_offset < 0xffffff)
offsize = 3;
else if (xref_offset < 0xffffffff)
offsize = 4;
else if (xref_offset < 0xffffffffff)
offsize = 5;
else if (xref_offset < 0xffffffffffff)
offsize = 6;
else if (xref_offset < 0xffffffffffffff)
offsize = 7;
else
offsize = 8;

for (i = 0; i < pdf->num_objs; i ++)
{
pdfio_obj_t *obj = pdf->objs[i]; // Current object
// Create the object...
if ((w_array = pdfioArrayCreate(pdf)) == NULL)
{
_pdfioFileError(pdf, "Unable to write cross-reference table.");
ret = false;
goto done;
}

pdfioArrayAppendNumber(w_array, 1);
pdfioArrayAppendNumber(w_array, offsize);
pdfioArrayAppendNumber(w_array, 1);

if (!_pdfioFilePrintf(pdf, "%010lu %05u n \n", (unsigned long)obj->offset, obj->generation))
if ((xref_dict = pdfioDictCreate(pdf)) == NULL)
{
_pdfioFileError(pdf, "Unable to write cross-reference table.");
ret = false;
goto done;
}
}

// Write the trailer...
if (!_pdfioFilePuts(pdf, "trailer\n"))
{
_pdfioFileError(pdf, "Unable to write trailer.");
ret = false;
goto done;
}
pdfioDictSetName(xref_dict, "Type", "XRef");
pdfioDictSetNumber(xref_dict, "Size", pdf->num_objs + 2);
pdfioDictSetArray(xref_dict, "W", w_array);
pdfioDictSetName(xref_dict, "Filter", "FlateDecode");

if ((pdf->trailer_dict = pdfioDictCreate(pdf)) == NULL)
{
_pdfioFileError(pdf, "Unable to create trailer.");
ret = false;
goto done;
}
if (pdf->encrypt_obj)
pdfioDictSetObj(xref_dict, "Encrypt", pdf->encrypt_obj);
if (pdf->id_array)
pdfioDictSetArray(xref_dict, "ID", pdf->id_array);
pdfioDictSetObj(xref_dict, "Info", pdf->info_obj);
pdfioDictSetObj(xref_dict, "Root", pdf->root_obj);

if ((xref_obj = pdfioFileCreateObj(pdf, xref_dict)) == NULL)
{
_pdfioFileError(pdf, "Unable to write cross-reference table.");
ret = false;
goto done;
}

if ((xref_st = pdfioObjCreateStream(xref_obj, PDFIO_FILTER_FLATE)) == NULL)
{
_pdfioFileError(pdf, "Unable to write cross-reference table.");
ret = false;
goto done;
}

// Write the "free" 0 object...
memset(buffer, 0, sizeof(buffer));
pdfioStreamWrite(xref_st, buffer, offsize + 2);

// Then write the "allocated" objects...
buffer[0] = 1;

for (i = 0; i < pdf->num_objs; i ++)
{
obj = pdf->objs[i]; // Current object

switch (offsize)
{
case 1 :
buffer[1] = obj->offset & 255;
break;
case 2 :
buffer[1] = (obj->offset >> 8) & 255;
buffer[2] = obj->offset & 255;
break;
case 3 :
buffer[1] = (obj->offset >> 16) & 255;
buffer[2] = (obj->offset >> 8) & 255;
buffer[3] = obj->offset & 255;
break;
case 4 :
buffer[1] = (obj->offset >> 24) & 255;
buffer[2] = (obj->offset >> 16) & 255;
buffer[3] = (obj->offset >> 8) & 255;
buffer[4] = obj->offset & 255;
break;
case 5 :
buffer[1] = (obj->offset >> 32) & 255;
buffer[2] = (obj->offset >> 24) & 255;
buffer[3] = (obj->offset >> 16) & 255;
buffer[4] = (obj->offset >> 8) & 255;
buffer[5] = obj->offset & 255;
break;
case 6 :
buffer[1] = (obj->offset >> 40) & 255;
buffer[2] = (obj->offset >> 32) & 255;
buffer[3] = (obj->offset >> 24) & 255;
buffer[4] = (obj->offset >> 16) & 255;
buffer[5] = (obj->offset >> 8) & 255;
buffer[6] = obj->offset & 255;
break;
case 7 :
buffer[1] = (obj->offset >> 48) & 255;
buffer[2] = (obj->offset >> 40) & 255;
buffer[3] = (obj->offset >> 32) & 255;
buffer[4] = (obj->offset >> 24) & 255;
buffer[5] = (obj->offset >> 16) & 255;
buffer[6] = (obj->offset >> 8) & 255;
buffer[7] = obj->offset & 255;
break;
default :
buffer[1] = (obj->offset >> 56) & 255;
buffer[2] = (obj->offset >> 48) & 255;
buffer[3] = (obj->offset >> 40) & 255;
buffer[4] = (obj->offset >> 32) & 255;
buffer[5] = (obj->offset >> 24) & 255;
buffer[6] = (obj->offset >> 16) & 255;
buffer[7] = (obj->offset >> 8) & 255;
buffer[8] = obj->offset & 255;
break;
}

if (pdf->encrypt_obj)
pdfioDictSetObj(pdf->trailer_dict, "Encrypt", pdf->encrypt_obj);
if (pdf->id_array)
pdfioDictSetArray(pdf->trailer_dict, "ID", pdf->id_array);
pdfioDictSetObj(pdf->trailer_dict, "Info", pdf->info_obj);
pdfioDictSetObj(pdf->trailer_dict, "Root", pdf->root_obj);
pdfioDictSetNumber(pdf->trailer_dict, "Size", pdf->num_objs + 1);
if (!pdfioStreamWrite(xref_st, buffer, offsize + 2))
{
_pdfioFileError(pdf, "Unable to write cross-reference table.");
ret = false;
goto done;
}
}

if (!_pdfioDictWrite(pdf->trailer_dict, NULL, NULL))
pdfioStreamClose(xref_st);
}
else
{
_pdfioFileError(pdf, "Unable to write trailer.");
ret = false;
goto done;
// Write a cross-reference table...
if (!_pdfioFilePrintf(pdf, "xref\n0 %lu \n0000000000 65535 f \n", (unsigned long)pdf->num_objs + 1))
{
_pdfioFileError(pdf, "Unable to write cross-reference table.");
ret = false;
goto done;
}

for (i = 0; i < pdf->num_objs; i ++)
{
obj = pdf->objs[i]; // Current object

if (!_pdfioFilePrintf(pdf, "%010lu %05u n \n", (unsigned long)obj->offset, obj->generation))
{
_pdfioFileError(pdf, "Unable to write cross-reference table.");
ret = false;
goto done;
}
}

// Write the trailer...
if (!_pdfioFilePuts(pdf, "trailer\n"))
{
_pdfioFileError(pdf, "Unable to write trailer.");
ret = false;
goto done;
}

if ((pdf->trailer_dict = pdfioDictCreate(pdf)) == NULL)
{
_pdfioFileError(pdf, "Unable to create trailer.");
ret = false;
goto done;
}

if (pdf->encrypt_obj)
pdfioDictSetObj(pdf->trailer_dict, "Encrypt", pdf->encrypt_obj);
if (pdf->id_array)
pdfioDictSetArray(pdf->trailer_dict, "ID", pdf->id_array);
pdfioDictSetObj(pdf->trailer_dict, "Info", pdf->info_obj);
pdfioDictSetObj(pdf->trailer_dict, "Root", pdf->root_obj);
pdfioDictSetNumber(pdf->trailer_dict, "Size", pdf->num_objs + 1);

if (!_pdfioDictWrite(pdf->trailer_dict, NULL, NULL))
{
_pdfioFileError(pdf, "Unable to write trailer.");
ret = false;
goto done;
}
}

if (!_pdfioFilePrintf(pdf, "\nstartxref\n%lu\n%%EOF\n", (unsigned long)xref_offset))
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