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Use separate in and out pointers in secp256k1_ec_pubkey_decompress

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Right now `secp256k1_ec_pubkey_decompress` takes an in/out pointer to
a public key and replaces the input key with its decompressed variant.
This forces users who store compressed keys in small (<65 byte) fixed
size buffers (for example, the Rust bindings do this) to explicitly
and wastefully copy their key to a larger buffer.

[API BREAK]
This commit is contained in:
Andrew Poelstra
2015-05-11 09:55:45 -05:00
parent 729badff14
commit 210ffed5cd
3 changed files with 28 additions and 13 deletions
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18
include/secp256k1.h
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@@ -262,18 +262,20 @@ SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create(
/** Decompress a public key.
* In: ctx: pointer to a context object (cannot be NULL)
* In/Out: pubkey: pointer to a 65-byte array to put the decompressed public key.
* It must contain a 33-byte or 65-byte public key already (cannot be NULL)
* pubkeylen: pointer to the size of the public key pointed to by pubkey (cannot be NULL)
* It will be updated to reflect the new size.
* Returns: 0: pubkey was invalid
* 1: pubkey was valid, and was replaced with its decompressed version
* In: pubkeyin: pointer to a 33-byte or 65-byte public key (cannot be NULL)
* In/Out: pubkeyout: pointer to a 65-byte array to put the decompressed public key (cannot be NULL)
* May alias pubkeyin.
* pubkeylen: pointer to the size of the public key pointed to by pubkeyin (cannot be NULL)
* It will be updated to reflect the size of the public key in pubkeyout.
* Returns: 0: pubkeyin was invalid
* 1: pubkeyin was valid, and pubkeyout is its decompressed version
*/
SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_decompress(
const secp256k1_context_t* ctx,
unsigned char *pubkey,
const unsigned char *pubkeyin,
unsigned char *pubkeyout,
int *pubkeylen
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Export a private key in DER format.
* In: ctx: pointer to a context object, initialized for signing (cannot be NULL)