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Understanding Index Header

Hi all,

I am writing a program that parses out the .git/index file. I am
reading the git index header documentation, but I seem to be getting
jibberish data.

The first 12 bytes are the signature, version and entries. Great so far.

Afterwards, I try to read the extension signature, which the
documentation says: "4-byte extension signature. If the first byte is
'A'..'Z' the
extension is optional and can be ignored.". I am getting jibberish. Is
this expected?

Then, the extension size comes back as 35560000 (after ntohl()). That
seems extremely high. My structure is as follows:

struct _indexfile_hdr {
        unsigned char   sig[4];         /* Always "DIRC" */
        uint32_t        version;        /* Version Number */
        uint32_t        entries;        /* Number of extensions */
        unsigned char   extsig[4];      /* Extension signature */
        uint32_t        extsize;        /* Size of the extension */
        uint8_t         sha[8];         /* SHA1 of index before checksum */
} __packed;

Am I doing something wrong? Is there some offset or padding that I missed?

Farhan Khan
PGP Fingerprint: B28D 2726 E2BC A97E 3854 5ABE 9A9F 00BC D525 16EE