使用zlib从pdf中提取文本

我使用该函数在pdf文件中查找文本并将该文本替换为另一个文本。问题是，当我进行膨胀，然后更改文本和收缩时，在最终的pdf中有时会遗漏一些文本或图形。这是一个错误在我的代码或zlib库不支持这个压缩或什么?

// Open the PDF source file:
FILE *pdfFile = fopen([sourceFile cStringUsingEncoding:NSUTF8StringEncoding], "rb");
if (pdfFile) {
// Get the file length:
int fseekres = fseek(pdfFile, 0, SEEK_END);
if (fseekres != 0) {
fclose(pdfFile);
return nil;
}
long filelen = ftell(pdfFile);
fseekres = fseek(pdfFile, 0, SEEK_SET);
if (fseekres != 0) {
fclose(pdfFile);
return nil;
}
char *buffer = new char[filelen];
size_t actualread = fread(buffer, filelen, 1, pdfFile);
if (actualread != 1) {
fclose(pdfFile);
return nil;
}
bool morestreams = true;
while (morestreams) {
size_t streamstart = [self findStringInBuffer:buffer search:(char *)"stream" buffersize:filelen];
size_t streamend = [self findStringInBuffer:buffer search:(char *)"endstream" buffersize:filelen];
[self saveFile:buffer len:streamstart + 7 fileName:[destFile cStringUsingEncoding:NSUTF8StringEncoding]];
if (streamstart > 0 && streamend > streamstart) {
streamstart += 6;
if (buffer[streamstart] == 0x0d && buffer[streamstart + 1] == 0x0a) {
streamstart += 2;
} else if (buffer[streamstart] == 0x0a) {
streamstart++;
}
if (buffer[streamend - 2] == 0x0d && buffer[streamend - 1] == 0x0a) {
streamend -= 2;
} else if (buffer[streamend - 1] == 0x0a) {
streamend--;
}
size_t outsize = (streamend - streamstart) * 10;
char *output = new char[outsize];
z_stream zstrm;
zstrm.zalloc = Z_NULL;
zstrm.zfree = Z_NULL;
zstrm.opaque = Z_NULL;
zstrm.avail_in = (uint)(streamend - streamstart + 1);
zstrm.avail_out = (uint)outsize;
zstrm.next_in = (Bytef *)(buffer + streamstart);
zstrm.next_out = (Bytef *)output;
int rsti = inflateInit(&zstrm);
if (rsti == Z_OK) {
int rst2 = inflate(&zstrm, Z_FINISH);
inflateEnd(&zstrm);
if (rst2 >= 0) {
size_t totout = zstrm.total_out;
//search and replace text code here
size_t coutsize = (streamend - streamstart + 1) * 10;
char *coutput = new char[coutsize];
z_stream c_stream;
c_stream.zalloc = Z_NULL;
c_stream.zfree = Z_NULL;
c_stream.opaque = Z_NULL;
c_stream.total_out = 0;
c_stream.avail_in = (uint)totout;
c_stream.avail_out = (uint)coutsize;
c_stream.next_in = (Bytef *)output;
c_stream.next_out = (Bytef *)coutput;
rsti = deflateInit(&c_stream, Z_DEFAULT_COMPRESSION);
if (rsti == Z_OK) {
rsti = deflate(&c_stream, Z_FINISH);
deflateEnd(&c_stream);
if (rsti >= 0) {
[self saveFile:coutput len:c_stream.total_out fileName:[destFile cStringUsingEncoding:NSUTF8StringEncoding]];
}
}
delete [] coutput; coutput = 0;
[self saveFile:(char *)"nendstr" len:7 fileName:[destFile cStringUsingEncoding:NSUTF8StringEncoding]];
}
}
delete[] output; output = 0;
buffer += streamend + 7;
filelen = filelen - (streamend + 7);
} else {
morestreams = false;
}
}
[self saveFile:buffer len:filelen fileName:[destFile cStringUsingEncoding:NSUTF8StringEncoding]];
}
fclose(pdfFile);