git/hex.c, branch v2.35.2

hex: print objects using the hash algorithm member

2021-04-27T07:31:39Z

Now that all code paths correctly set the hash algorithm member of struct object_id, write an object's hex representation using the hash algorithm member embedded in it. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

hex: default to the_hash_algo on zero algorithm value

2021-04-27T07:31:39Z

There are numerous places in the codebase where we assume we can initialize data by zeroing all its bytes. However, when we do that with a struct object_id, it leaves the structure with a zero value for the algorithm, which is invalid. We could forbid this pattern and require that all struct object_id instances be initialized using oidclr, but this seems burdensome and it's unnatural to most C programmers. Instead, if the algorithm is zero, assume we wanted to use the default hash algorithm instead. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

hash: set, copy, and use algo field in struct object_id

2021-04-27T07:31:38Z

Now that struct object_id has an algorithm field, we should populate it. This will allow us to handle object IDs in any supported algorithm and distinguish between them. Ensure that the field is written whenever we write an object ID by storing it explicitly every time we write an object. Set values for the empty blob and tree values as well. In addition, use the algorithm field to compare object IDs. Note that because we zero-initialize struct object_id in many places throughout the codebase, we default to the default algorithm in cases where the algorithm field is zero rather than explicitly initialize all of those locations. This leads to a branch on every comparison, but the alternative is to compare the entire buffer each time and padding the buffer for SHA-1. That alternative ranges up to 3.9% worse than this approach on the perf t0001, t1450, and t1451. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

hex: add functions to parse hex object IDs in any algorithm

2020-02-24T17:33:21Z

There are some places where we need to parse a hex object ID in any algorithm without knowing beforehand which algorithm is in use. An example is when parsing fast-import marks. Add a get_oid_hex_any to parse an object ID and return the algorithm it belongs to, and additionally add parse_oid_hex_any which is the equivalent change for parse_oid_hex. If the object is not parseable, we return GIT_HASH_UNKNOWN. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

hex: introduce parsing variants taking hash algorithms

2020-02-24T17:33:21Z

Introduce variants of get_oid_hex and parse_oid_hex that parse an arbitrary hash algorithm, implementing internal functions to avoid duplication. These functions can be used in the transport code to parse refs properly. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

hex: drop sha1_to_hex()

2019-11-13T01:09:10Z

There's only a single caller left of sha1_to_hex(), since everybody that has an object name in "unsigned char[]" now uses hash_to_hex() instead. This case is in the sha1dc wrapper, where we print a hex sha1 when we find a collision. This one will always be sha1, regardless of the current hash algorithm, so we can't use hash_to_hex() here. In practice we'd probably not be running sha1 at all if it isn't the current algorithm, but it's possible we might still occasionally need to compute a sha1 in a post-sha256 world. Since sha1_to_hex() is just a wrapper for hash_to_hex_algop(), let's call that ourselves. There's value in getting rid of the sha1-specific wrapper to de-clutter the global namespace, and to make sure nobody uses it (and as with sha1_to_hex_r() in the previous patch, we'll drop the coccinelle transformations, too). The sha1_to_hex() function is mentioned in a comment; we can easily swap that out for oid_to_hex() to give a better example. Also update the comment that was left stale when we added "struct object_id *" as a way to name an object and added functions to convert it to hex. The function is also mentioned in some test vectors in t4100, but that's not runnable code, so there's no point in trying to clean it up. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

hex: drop sha1_to_hex_r()

2019-11-11T09:11:41Z

There are no callers left; everybody uses oid_to_hex_r() or hash_to_hex_algop_r(). This used to actually be the underlying implementation for oid_to_hex_r(), but that's no longer the case since 47edb64997 (hex: introduce functions to print arbitrary hashes, 2018-11-14). Let's get rid of it to de-clutter and to make sure nobody uses it. Likewise we can drop the coccinelle rules that mention it, since the compiler will make it quite clear that the code does not work. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

hex: introduce functions to print arbitrary hashes

2018-11-14T07:54:52Z

Currently, we have functions that turn an arbitrary SHA-1 value or an object ID into hex format, either using a static buffer or with a user-provided buffer. Add variants of these functions that can handle an arbitrary hash algorithm, specified by constant. Update the documentation as well. While we're at it, remove the "extern" declaration from this family of functions, since it's not needed and our style now recommends against it. We use the variant taking the algorithm structure pointer as the internal variant, since taking an algorithm pointer is the easiest way to handle all of the variants in use. Note that we maintain these functions because there are hashes which must change based on the hash algorithm in use but are not object IDs (such as pack checksums). Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

hex: switch to using the_hash_algo

2018-07-16T21:27:39Z

Instead of using the GIT_SHA1_* constants, switch to using the_hash_algo to convert object IDs to and from hex format. Signed-off-by: brian m. carlson Signed-off-by: Junio C Hamano

notes: move hex_to_bytes() to hex.c and export it

2017-11-01T01:35:35Z

Make the function for converting pairs of hexadecimal digits to binary available to other call sites. Signed-off-by: Rene Scharfe Signed-off-by: Junio C Hamano