zLib on iPhone, stop at first BLOCK
- by cedric
I am trying to call iPhone zLib to decompress the zlib stream from our HTTP based server, but the code always stop after finishing the first zlib block.
Obviously, iPhone SDK is using the standard open Zlib. My doubt is that the parameter for inflateInit2 is not appropriate here.
I spent lots of time reading the zlib manual, but it isn't that helpful.
Here is the details, your help is appreciated.
(1) the HTTP request:
NSURL *url = [NSURL URLWithString:@"http://192.168.0.98:82/WIC?query=getcontacts&PIN=12345678&compression=Y"];
(2) The data I get from server is something like this (if decompressed). The stream was compressed by C# zlib class DeflateStream:
$REC_TYPE=SYS
Status=OK
Message=OK
SetID=
IsLast=Y
StartIndex=0
LastIndex=6
EOR
......
$REC_TYPE=CONTACTSDISTLIST
ID=2
Name=CTU+L%2EA%2E
OnCallEnabled=Y
OnCallMinUsers=1
OnCallEditRight=
OnCallEditDLRight=D
Fields=
CL=
OnCallStatus=
EOR
(3) However, I will only get the first Block. The code for decompression on iPhone (copied from a code piece from somewhere here) is as follow.
The loop between Line 23~38 always break the second time execution.
+ (NSData *) uncompress: (NSData*) data
{
1 if ([data length] == 0) return nil;
2 NSInteger length = [data length];
3 unsigned full_length = length;
4 unsigned half_length =length/ 2;
5 NSMutableData *decompressed = [NSMutableData dataWithLength: 5*full_length + half_length];
6 BOOL done = NO;
7 int status;
8 z_stream strm;
9 length=length-4;
10 void* bytes= malloc(length);
11 NSRange range;
12 range.location=4;
13 range.length=length;
14 [data getBytes: bytes range: range];
15 strm.next_in = bytes;
16 strm.avail_in = length;
17 strm.total_out = 0;
18 strm.zalloc = Z_NULL;
19 strm.zfree = Z_NULL;
20 strm.data_type= Z_BINARY;
21 // if (inflateInit(&strm) != Z_OK) return nil;
22 if (inflateInit2(&strm, (-15)) != Z_OK) return nil; //It won't work if change -15 to positive numbers.
23 while (!done)
24 {
25 // Make sure we have enough room and reset the lengths.
26 if (strm.total_out >= [decompressed length])
27 [decompressed increaseLengthBy: half_length];
28 strm.next_out = [decompressed mutableBytes] + strm.total_out;
29 strm.avail_out = [decompressed length] - strm.total_out;
30
31 // Inflate another chunk.
32 status = inflate (&strm, Z_SYNC_FLUSH); //Z_SYNC_FLUSH-->Z_BLOCK, won't work either
33 if (status == Z_STREAM_END){
34
35 done = YES;
36 }
37 else if (status != Z_OK) break;
38 }
39 if (inflateEnd (&strm) != Z_OK) return nil;
40 // Set real length.
41 if (done)
42 {
43 [decompressed setLength: strm.total_out];
44 return [NSData dataWithData: decompressed];
45 }
46 else return nil;
47 }
