wim_recalculate_refcnts(): Check for error

[wimlib] / src / wim.c

diff --git a/src/wim.c b/src/wim.c
index 63459751eff443c74ccb06e30c7ba1059573aff8..2f5f5e0e8e27d534c49db96b8af3fad442f9a9f4 100644 (file)
--- a/src/wim.c
+++ b/src/wim.c
@@ -75,6 +75,7 @@ new_wim_struct(void)
        return wim;
 }
 
+/* Determine if the chunk size is valid for the specified compression type.  */
 static bool
 wim_chunk_size_valid(u32 chunk_size, int ctype)
 {
@@ -109,9 +110,19 @@ wim_chunk_size_valid(u32 chunk_size, int ctype)
         */
        switch (ctype) {
        case WIMLIB_COMPRESSION_TYPE_LZX:
-               /* TODO: Allow other chunk sizes when supported by the LZX
-                * compressor and decompressor.  */
-               return order == 15;
+               /* For LZX compression, the chunk size corresponds to the LZX
+                * window size, which according the LZX specification can be any
+                * power of 2 between 2^15 and 2^21, inclusively.  All these are
+                * supported by wimlib; however, unfortunately only 2^15 is
+                * supported by WIMGAPI[1] so this value is used by default.
+                *
+                * [1] WIMGAPI (Windows 7) attempts to decompress LZX chunk
+                * sizes > 2^15 but seems to have bug(s) that cause it to fail
+                * or crash.  (I tried several tweaks to the LZX data but none
+                * resulted in successful decompression.)  WIMGAPI (Windows 8)
+                * appears to refuse to open WIMs with chunk size > 2^15
+                * entirely.  */
+               return order >= 15 && order <= 21;
 
        case WIMLIB_COMPRESSION_TYPE_XPRESS:
                /* WIMGAPI (Windows 7) didn't seem to support XPRESS chunk size
@@ -119,12 +130,21 @@ wim_chunk_size_valid(u32 chunk_size, int ctype)
                 * supported.  67108864 was the largest size that worked.
                 * (Note, however, that the offsets of XPRESS matches are still
                 * limited to 65535 bytes even when a much larger chunk size is
-                * used!)  */
+                * used!)
+                *
+                * WIMGAPI (Windows 8) seemed to have removed the support for
+                * larger XPRESS chunk sizes and will refuse to open such WIMs.
+                *
+                * 2^15 = 32768 is the default value used for compatibility, but
+                * wimlib can actually use up to 2^26.  */
                return order >= 15 && order <= 26;
        }
        return false;
 }
 
+/* Return the default chunk size to use for the specified compression type.
+ *
+ * See notes above in wim_chunk_size_valid().  */
 static u32
 wim_default_chunk_size(int ctype)
 {
@@ -447,14 +467,21 @@ wimlib_set_output_chunk_size(WIMStruct *wim, uint32_t chunk_size)
                      wimlib_get_compression_type_string(wim->out_compression_type));
                switch (wim->out_compression_type) {
                case WIMLIB_COMPRESSION_TYPE_XPRESS:
-                       ERROR("Valid chunk sizes for XPRESS are 32768, 65536, 131072, ..., 67108864.");
+                       ERROR("Valid chunk sizes for XPRESS are "
+                             "32768, 65536, 131072, ..., 67108864.");
                        break;
                case WIMLIB_COMPRESSION_TYPE_LZX:
-                       ERROR("Valid chunk sizes for XPRESS are 65536.");
+                       ERROR("Valid chunk sizes for LZX are "
+                             "32768, 65536, 131072, ..., 2097152.");
                        break;
                }
                return WIMLIB_ERR_INVALID_CHUNK_SIZE;
        }
+       if (chunk_size != 32768) {
+               WARNING  ("Changing the compression chunk size to any value other than\n"
+               "          the default of 32768 bytes eliminates compatibility with\n"
+               "          Microsoft's software!");
+       }
        wim->out_chunk_size = chunk_size;
        return 0;
 }
@@ -860,8 +887,11 @@ can_delete_from_wim(WIMStruct *wim)
        ret = can_modify_wim(wim);
        if (ret)
                return ret;
-       if (!wim->refcnts_ok)
-               wim_recalculate_refcnts(wim);
+       if (!wim->refcnts_ok) {
+               ret = wim_recalculate_refcnts(wim);
+               if (ret)
+                       return ret;
+       }
        return 0;
 }