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builtins.convertHash

convertHash

builtins.convertHash

Primop
Docs pulled from | This Revision | about 19 hours ago

Nix manual

Takes 1 arguments

args

Return the specified representation of a hash string, based on the attributes presented in args:

  • hash

    The hash to be converted. The hash format is detected automatically.

  • hashAlgo

    The algorithm used to create the hash. Must be one of

    • "md5"
    • "sha1"
    • "sha256"
    • "sha512"

    The attribute may be omitted when hash is an SRI hash or when the hash is prefixed with the hash algorithm name followed by a colon. That <hashAlgo>:<hashBody> syntax is supported for backwards compatibility with existing tooling.

  • toHashFormat

    The format of the resulting hash. Must be one of

    • "base16"
    • "nix32"
    • "base32" (deprecated alias for "nix32")
    • "base64"
    • "sri"

The result hash is the toHashFormat representation of the hash hash.

Example

Convert a SHA256 hash in Base16 to SRI:

builtins.convertHash {
  hash = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
  toHashFormat = "sri";
  hashAlgo = "sha256";
}

"sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU="

Example

Convert a SHA256 hash in SRI to Base16:

builtins.convertHash {
  hash = "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=";
  toHashFormat = "base16";
}

"e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"

Example

Convert a hash in the form <hashAlgo>:<hashBody> in Base16 to SRI:

builtins.convertHash {
  hash = "sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855";
  toHashFormat = "sri";
}

"sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU="

Noogle detected

Aliases

Implementation

This function is implemented in c++ and is part of the native nix runtime.

src/libexpr/primops.cc:4788

static void prim_convertHash(EvalState & state, const PosIdx pos, Value ** args, Value & v)
{
    state.forceAttrs(*args[0], pos, "while evaluating the first argument passed to builtins.convertHash");
    auto inputAttrs = args[0]->attrs();

    auto iteratorHash = state.getAttr(state.symbols.create("hash"), inputAttrs, "while locating the attribute 'hash'");
    auto hash = state.forceStringNoCtx(*iteratorHash->value, pos, "while evaluating the attribute 'hash'");

    auto iteratorHashAlgo = inputAttrs->get(state.symbols.create("hashAlgo"));
    std::optional<HashAlgorithm> ha = std::nullopt;
    if (iteratorHashAlgo)
        ha = parseHashAlgo(
            state.forceStringNoCtx(*iteratorHashAlgo->value, pos, "while evaluating the attribute 'hashAlgo'"));

    auto iteratorToHashFormat = state.getAttr(
        state.symbols.create("toHashFormat"), args[0]->attrs(), "while locating the attribute 'toHashFormat'");
    HashFormat hf = parseHashFormat(
        state.forceStringNoCtx(*iteratorToHashFormat->value, pos, "while evaluating the attribute 'toHashFormat'"));

    v.mkString(Hash::parseAny(hash, ha).to_string(hf, hf == HashFormat::SRI), state.mem);
}