Function WriteHmap

tools/gyp/pylib/gyp/mac_tool.py:690–761

Generates a header map based on |filelist|. Per Mark Mentovai: A header map is structured essentially as a hash table, keyed by names used in #includes, and providing pathnames to the actual files. The implementation below and the comment above comes from inspecting: http

(output_name, filelist)

def WriteHmap(output_name, filelist):
    """Generates a header map based on |filelist|.

    Per Mark Mentovai:
      A header map is structured essentially as a hash table, keyed by names used
      in #includes, and providing pathnames to the actual files.

    The implementation below and the comment above comes from inspecting:
      http://www.opensource.apple.com/source/distcc/distcc-2503/distcc_dist/include_server/headermap.py?txt
    while also looking at the implementation in clang in:
      https://llvm.org/svn/llvm-project/cfe/trunk/lib/Lex/HeaderMap.cpp
    """
    magic = 1751998832
    version = 1
    _reserved = 0
    count = len(filelist)
    capacity = NextGreaterPowerOf2(count)
    strings_offset = 24 + (12 * capacity)
    max_value_length = max(len(value) for value in filelist.values())

    out = open(output_name, "wb")
    out.write(
        struct.pack(
            "<LHHLLLL",
            magic,
            version,
            _reserved,
            strings_offset,
            count,
            capacity,
            max_value_length,
        )
    )

    # Create empty hashmap buckets.
    buckets = [None] * capacity
    for file, path in filelist.items():
        key = 0
        for c in file:
            key += ord(c.lower()) * 13

        # Fill next empty bucket.
        while buckets[key & capacity - 1] is not None:
            key = key + 1
        buckets[key & capacity - 1] = (file, path)

    next_offset = 1
    for bucket in buckets:
        if bucket is None:
            out.write(struct.pack("<LLL", 0, 0, 0))
        else:
            (file, path) = bucket
            key_offset = next_offset
            prefix_offset = key_offset + len(file) + 1
            suffix_offset = prefix_offset + len(os.path.dirname(path) + os.sep) + 1
            next_offset = suffix_offset + len(os.path.basename(path)) + 1
            out.write(struct.pack("<LLL", key_offset, prefix_offset, suffix_offset))