path: root/xpcom/reflect/xptinfo/xptcodegen.py

#!/usr/bin/env python
# jsonlink.py - Merge JSON typelib files into a .cpp file
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.

import json
from collections import OrderedDict

import buildconfig
from mozbuild.util import memoize
from perfecthash import PerfectHash

# Pick a nice power-of-two size for our intermediate PHF tables.
PHFSIZE = 512


def indented(s):
    return s.replace("\n", "\n  ")


def cpp(v):
    if type(v) == bool:
        return "true" if v else "false"
    return str(v)


def mkstruct(*fields):
    def mk(comment, **vals):
        assert len(fields) == len(vals)
        r = "{ // " + comment
        r += indented(",".join("\n/* %s */ %s" % (k, cpp(vals[k])) for k in fields))
        r += "\n}"
        return r

    return mk


##########################################################
# Ensure these fields are in the same order as xptinfo.h #
##########################################################
nsXPTInterfaceInfo = mkstruct(
    "mIID",
    "mName",
    "mParent",
    "mBuiltinClass",
    "mMainProcessScriptableOnly",
    "mMethods",
    "mConsts",
    "mFunction",
    "mNumMethods",
    "mNumConsts",
)

##########################################################
# Ensure these fields are in the same order as xptinfo.h #
##########################################################
nsXPTType = mkstruct(
    "mTag",
    "mInParam",
    "mOutParam",
    "mOptionalParam",
    "mData1",
    "mData2",
)

##########################################################
# Ensure these fields are in the same order as xptinfo.h #
##########################################################
nsXPTParamInfo = mkstruct(
    "mType",
)

##########################################################
# Ensure these fields are in the same order as xptinfo.h #
##########################################################
nsXPTMethodInfo = mkstruct(
    "mName",
    "mParams",
    "mNumParams",
    "mGetter",
    "mSetter",
    "mReflectable",
    "mOptArgc",
    "mContext",
    "mHasRetval",
    "mIsSymbol",
)

##########################################################
# Ensure these fields are in the same order as xptinfo.h #
##########################################################
nsXPTDOMObjectInfo = mkstruct(
    "mUnwrap",
    "mWrap",
    "mCleanup",
)

##########################################################
# Ensure these fields are in the same order as xptinfo.h #
##########################################################
nsXPTConstantInfo = mkstruct(
    "mName",
    "mSigned",
    "mValue",
)


# Helper functions for dealing with IIDs.
#
# Unfortunately, the way we represent IIDs in memory depends on the endianness
# of the target architecture. We store an nsIID as a 16-byte, 4-tuple of:
#
#   (uint32_t, uint16_t, uint16_t, [uint8_t; 8])
#
# Unfortunately, this means that when we hash the bytes of the nsIID on a
# little-endian target system, we need to hash them in little-endian order.
# These functions let us split the input hexadecimal string into components,
# encoding each as a little-endian value, and producing an accurate bytearray.
#
# It would be nice to have a consistent representation of IIDs in memory such
# that we don't have to do these gymnastics to get an accurate hash.


def split_at_idxs(s, lengths):
    idx = 0
    for length in lengths:
        yield s[idx : idx + length]
        idx += length
    assert idx == len(s)


def split_iid(iid):  # Get the individual components out of an IID string.
    iid = iid.replace("-", "")  # Strip any '-' delimiters
    return tuple(split_at_idxs(iid, (8, 4, 4, 2, 2, 2, 2, 2, 2, 2, 2)))


@memoize
def iid_bytes(iid):  # Get the byte representation of the IID for hashing.
    bs = bytearray()
    for num in split_iid(iid):
        b = bytearray.fromhex(num)
        # Match endianness of the target platform for each component
        if buildconfig.substs["TARGET_ENDIANNESS"] == "little":
            b.reverse()
        bs += b
    return bs


# Split a 16-bit integer into its high and low 8 bits
def splitint(i):
    assert i < 2**16
    return (i >> 8, i & 0xFF)


# Occasionally in xpconnect, we need to fabricate types to pass into the
# conversion methods. In some cases, these types need to be arrays, which hold
# indicies into the extra types array.
#
# These are some types which should have known indexes into the extra types
# array.
utility_types = [
    {"tag": "TD_INT8"},
    {"tag": "TD_UINT8"},
    {"tag": "TD_INT16"},
    {"tag": "TD_UINT16"},
    {"tag": "TD_INT32"},
    {"tag": "TD_UINT32"},
    {"tag": "TD_INT64"},
    {"tag": "TD_UINT64"},
    {"tag": "TD_FLOAT"},
    {"tag": "TD_DOUBLE"},
    {"tag": "TD_BOOL"},
    {"tag": "TD_CHAR"},
    {"tag": "TD_WCHAR"},
    {"tag": "TD_NSIDPTR"},
    {"tag": "TD_PSTRING"},
    {"tag": "TD_PWSTRING"},
    {"tag": "TD_INTERFACE_IS_TYPE", "iid_is": 0},
]


# Core of the code generator. Takes a list of raw JSON XPT interfaces, and
# writes out a file containing the necessary static declarations into fd.
def link_to_cpp(interfaces, fd, header_fd):
    # Perfect Hash from IID to interface.
    iid_phf = PerfectHash(interfaces, PHFSIZE, key=lambda i: iid_bytes(i["uuid"]))
    for idx, iface in enumerate(iid_phf.entries):
        iface["idx"] = idx  # Store the index in iid_phf of the entry.

    # Perfect Hash from name to iid_phf index.
    name_phf = PerfectHash(interfaces, PHFSIZE, key=lambda i: i["name"].encode("ascii"))

    def interface_idx(name):
        entry = name and name_phf.get_entry(name.encode("ascii"))
        if entry:
            return entry["idx"] + 1  # 1-based, use 0 as a sentinel.
        return 0

    # NOTE: State used while linking. This is done with closures rather than a
    # class due to how this file's code evolved.
    includes = set()
    types = []
    type_cache = {}
    params = []
    param_cache = {}
    methods = []
    max_params = 0
    method_with_max_params = None
    consts = []
    domobjects = []
    domobject_cache = {}
    strings = OrderedDict()

    def lower_uuid(uuid):
        return (
            "{0x%s, 0x%s, 0x%s, {0x%s, 0x%s, 0x%s, 0x%s, 0x%s, 0x%s, 0x%s, 0x%s}}"
            % split_iid(uuid)
        )

    def lower_domobject(do):
        assert do["tag"] == "TD_DOMOBJECT"

        idx = domobject_cache.get(do["name"])
        if idx is None:
            idx = domobject_cache[do["name"]] = len(domobjects)

            includes.add(do["headerFile"])
            domobjects.append(
                nsXPTDOMObjectInfo(
                    "%d = %s" % (idx, do["name"]),
                    # These methods are defined at the top of the generated file.
                    mUnwrap="UnwrapDOMObject<mozilla::dom::prototypes::id::%s, %s>"
                    % (do["name"], do["native"]),
                    mWrap="WrapDOMObject<%s>" % do["native"],
                    mCleanup="CleanupDOMObject<%s>" % do["native"],
                )
            )

        return idx

    def lower_string(s):
        if s in strings:
            # We've already seen this string.
            return strings[s]
        elif len(strings):
            # Get the last string we inserted (should be O(1) on OrderedDict).
            last_s = next(reversed(strings))
            strings[s] = strings[last_s] + len(last_s) + 1
        else:
            strings[s] = 0
        return strings[s]

    def lower_symbol(s):
        return "uint32_t(JS::SymbolCode::%s)" % s

    def lower_extra_type(type):
        key = describe_type(type)
        idx = type_cache.get(key)
        if idx is None:
            idx = type_cache[key] = len(types)
            # Make sure `types` is the proper length for any recursive calls
            # to `lower_extra_type` that might happen from within `lower_type`.
            types.append(None)
            realtype = lower_type(type)
            types[idx] = realtype
        return idx

    def describe_type(type):  # Create the type's documentation comment.
        tag = type["tag"][3:].lower()
        if tag == "legacy_array":
            return "%s[size_is=%d]" % (describe_type(type["element"]), type["size_is"])
        elif tag == "array":
            return "Array<%s>" % describe_type(type["element"])
        elif tag == "interface_type" or tag == "domobject":
            return type["name"]
        elif tag == "interface_is_type":
            return "iid_is(%d)" % type["iid_is"]
        elif tag.endswith("_size_is"):
            return "%s(size_is=%d)" % (tag, type["size_is"])
        return tag

    def lower_type(type, in_=False, out=False, optional=False):
        tag = type["tag"]
        d1 = d2 = 0

        if tag == "TD_LEGACY_ARRAY":
            d1 = type["size_is"]
            d2 = lower_extra_type(type["element"])

        elif tag == "TD_ARRAY":
            # NOTE: TD_ARRAY can hold 16 bits of type index, while
            # TD_LEGACY_ARRAY can only hold 8.
            d1, d2 = splitint(lower_extra_type(type["element"]))

        elif tag == "TD_INTERFACE_TYPE":
            d1, d2 = splitint(interface_idx(type["name"]))

        elif tag == "TD_INTERFACE_IS_TYPE":
            d1 = type["iid_is"]

        elif tag == "TD_DOMOBJECT":
            d1, d2 = splitint(lower_domobject(type))

        elif tag.endswith("_SIZE_IS"):
            d1 = type["size_is"]

        assert d1 < 256 and d2 < 256, "Data values too large"
        return nsXPTType(
            describe_type(type),
            mTag=tag,
            mData1=d1,
            mData2=d2,
            mInParam=in_,
            mOutParam=out,
            mOptionalParam=optional,
        )

    def lower_param(param, paramname):
        params.append(
            nsXPTParamInfo(
                "%d = %s" % (len(params), paramname),
                mType=lower_type(
                    param["type"],
                    in_="in" in param["flags"],
                    out="out" in param["flags"],
                    optional="optional" in param["flags"],
                ),
            )
        )

    def is_type_reflectable(type):
        # All native types end up getting tagged as void*, or as wrapper types around void*
        if type["tag"] == "TD_VOID":
            return False
        if type["tag"] in ("TD_ARRAY", "TD_LEGACY_ARRAY"):
            return is_type_reflectable(type["element"])
        return True

    def is_method_reflectable(method):
        if "hidden" in method["flags"]:
            return False

        for param in method["params"]:
            # Reflected methods can't use non-reflectable types.
            if not is_type_reflectable(param["type"]):
                return False

        return True

    def lower_method(method, ifacename, builtinclass):
        methodname = "%s::%s" % (ifacename, method["name"])

        isSymbol = "symbol" in method["flags"]
        reflectable = is_method_reflectable(method)

        if not reflectable and builtinclass:
            # Hide the parameters of methods that can't be called from JS and
            # are on builtinclass interfaces to reduce the size of the file.
            paramidx = name = numparams = 0
        else:
            if isSymbol:
                name = lower_symbol(method["name"])
            else:
                name = lower_string(method["name"])

            numparams = len(method["params"])

            # Check cache for parameters
            cachekey = json.dumps(method["params"], sort_keys=True)
            paramidx = param_cache.get(cachekey)
            if paramidx is None:
                paramidx = param_cache[cachekey] = len(params)
                for idx, param in enumerate(method["params"]):
                    lower_param(param, "%s[%d]" % (methodname, idx))

        nonlocal max_params, method_with_max_params
        if numparams > max_params:
            max_params = numparams
            method_with_max_params = methodname
        methods.append(
            nsXPTMethodInfo(
                "%d = %s" % (len(methods), methodname),
                mName=name,
                mParams=paramidx,
                mNumParams=numparams,
                # Flags
                mGetter="getter" in method["flags"],
                mSetter="setter" in method["flags"],
                mReflectable=reflectable,
                mOptArgc="optargc" in method["flags"],
                mContext="jscontext" in method["flags"],
                mHasRetval="hasretval" in method["flags"],
                mIsSymbol=isSymbol,
            )
        )

    def lower_const(const, ifacename):
        assert const["type"]["tag"] in [
            "TD_INT16",
            "TD_INT32",
            "TD_UINT8",
            "TD_UINT16",
            "TD_UINT32",
        ]
        is_signed = const["type"]["tag"] in ["TD_INT16", "TD_INT32"]

        # Constants are always either signed or unsigned 16 or 32 bit integers,
        # which we will only need to convert to JS values. To save on space,
        # don't bother storing the type, and instead just store a 32-bit
        # unsigned integer, and stash whether to interpret it as signed.
        consts.append(
            nsXPTConstantInfo(
                "%d = %s::%s" % (len(consts), ifacename, const["name"]),
                mName=lower_string(const["name"]),
                mSigned=is_signed,
                mValue="(uint32_t)%d" % const["value"],
            )
        )

    def ancestors(iface):
        yield iface
        while iface["parent"]:
            iface = name_phf.get_entry(iface["parent"].encode("ascii"))
            yield iface

    def lower_iface(iface):
        method_cnt = sum(len(i["methods"]) for i in ancestors(iface))
        const_cnt = sum(len(i["consts"]) for i in ancestors(iface))

        # The number of maximum methods is not arbitrary. It is the same value
        # as in xpcom/reflect/xptcall/genstubs.pl; do not change this value
        # without changing that one or you WILL see problems.
        #
        # In addition, mNumMethods and mNumConsts are stored as a 8-bit ints,
        # meaning we cannot exceed 255 methods/consts on any interface.
        assert method_cnt < 250, "%s has too many methods" % iface["name"]
        assert const_cnt < 256, "%s has too many constants" % iface["name"]

        builtinclass = "builtinclass" in iface["flags"]

        # Store the lowered interface as 'cxx' on the iface object.
        iface["cxx"] = nsXPTInterfaceInfo(
            "%d = %s" % (iface["idx"], iface["name"]),
            mIID=lower_uuid(iface["uuid"]),
            mName=lower_string(iface["name"]),
            mParent=interface_idx(iface["parent"]),
            mMethods=len(methods),
            mNumMethods=method_cnt,
            mConsts=len(consts),
            mNumConsts=const_cnt,
            # Flags
            mBuiltinClass=builtinclass,
            mMainProcessScriptableOnly="main_process_only" in iface["flags"],
            mFunction="function" in iface["flags"],
        )

        # Lower methods and constants used by this interface
        for method in iface["methods"]:
            lower_method(method, iface["name"], builtinclass)
        for const in iface["consts"]:
            lower_const(const, iface["name"])

    # Lower the types which have fixed indexes first, and check that the indexes
    # seem correct.
    for expected, ty in enumerate(utility_types):
        got = lower_extra_type(ty)
        assert got == expected, "Wrong index when lowering"

    # Lower interfaces in the order of the IID phf's entries lookup.
    for iface in iid_phf.entries:
        lower_iface(iface)

    # Write out the final output files
    fd.write("/* THIS FILE WAS GENERATED BY xptcodegen.py - DO NOT EDIT */\n\n")
    header_fd.write("/* THIS FILE WAS GENERATED BY xptcodegen.py - DO NOT EDIT */\n\n")

    header_fd.write(
        """
#ifndef xptdata_h
#define xptdata_h

enum class nsXPTInterface : uint16_t {
"""
    )

    for entry in iid_phf.entries:
        header_fd.write("  %s,\n" % entry["name"])

    header_fd.write(
        """
};

#endif
"""
    )

    # Include any bindings files which we need to include for webidl types
    for include in sorted(includes):
        fd.write('#include "%s"\n' % include)

    # Write out our header
    fd.write(
        """
#include "xptinfo.h"
#include "mozilla/PerfectHash.h"
#include "mozilla/dom/BindingUtils.h"

// These template methods are specialized to be used in the sDOMObjects table.
template<mozilla::dom::prototypes::ID PrototypeID, typename T>
static nsresult UnwrapDOMObject(JS::Handle<JS::Value> aHandle, void** aObj, JSContext* aCx)
{
  RefPtr<T> p;
  nsresult rv = mozilla::dom::UnwrapObject<PrototypeID, T>(aHandle, p, aCx);
  p.forget(aObj);
  return rv;
}

template<typename T>
static bool WrapDOMObject(JSContext* aCx, void* aObj, JS::MutableHandle<JS::Value> aHandle)
{
  return mozilla::dom::GetOrCreateDOMReflector(aCx, reinterpret_cast<T*>(aObj), aHandle);
}

template<typename T>
static void CleanupDOMObject(void* aObj)
{
  RefPtr<T> p = already_AddRefed<T>(reinterpret_cast<T*>(aObj));
}

namespace xpt {
namespace detail {

"""
    )

    # Static data arrays
    def array(ty, name, els):
        fd.write(
            "const %s %s[] = {%s\n};\n\n"
            % (ty, name, ",".join(indented("\n" + str(e)) for e in els))
        )

    array("nsXPTType", "sTypes", types)
    array("nsXPTParamInfo", "sParams", params)
    array("nsXPTMethodInfo", "sMethods", methods)
    # Verify that stack-allocated buffers will do for xptcall implementations.
    msg = (
        "Too many method arguments in %s. "
        "Either reduce the number of arguments "
        "or increase PARAM_BUFFER_COUNT." % method_with_max_params
    )
    fd.write('static_assert(%s <= PARAM_BUFFER_COUNT, "%s");\n\n' % (max_params, msg))
    array("nsXPTDOMObjectInfo", "sDOMObjects", domobjects)
    array("nsXPTConstantInfo", "sConsts", consts)

    # The strings array. We write out individual characters to avoid MSVC restrictions.
    fd.write("const char sStrings[] = {\n")
    for s, off in strings.items():
        fd.write("  // %d = %s\n  '%s','\\0',\n" % (off, s, "','".join(s)))
    fd.write("};\n\n")

    # Build the perfect hash table for InterfaceByIID
    fd.write(
        iid_phf.cxx_codegen(
            name="InterfaceByIID",
            entry_type="nsXPTInterfaceInfo",
            entries_name="sInterfaces",
            lower_entry=lambda iface: iface["cxx"],
            # Check that the IIDs match to support IID keys not in the map.
            return_type="const nsXPTInterfaceInfo*",
            return_entry="return entry.IID().Equals(aKey) ? &entry : nullptr;",
            key_type="const nsIID&",
            key_bytes="reinterpret_cast<const char*>(&aKey)",
            key_length="sizeof(nsIID)",
        )
    )
    fd.write("\n")

    # Build the perfect hash table for InterfaceByName
    fd.write(
        name_phf.cxx_codegen(
            name="InterfaceByName",
            entry_type="uint16_t",
            lower_entry=lambda iface: "%-4d /* %s */" % (iface["idx"], iface["name"]),
            # Get the actual nsXPTInterfaceInfo from sInterfaces, and
            # double-check that names match.
            return_type="const nsXPTInterfaceInfo*",
            return_entry="return strcmp(sInterfaces[entry].Name(), aKey) == 0"
            " ? &sInterfaces[entry] : nullptr;",
        )
    )
    fd.write("\n")

    # Generate some checks that the indexes for the utility types match the
    # declared ones in xptinfo.h
    for idx, ty in enumerate(utility_types):
        fd.write(
            'static_assert(%d == (uint8_t)nsXPTType::Idx::%s, "Bad idx");\n'
            % (idx, ty["tag"][3:])
        )

    fd.write(
        """
const uint16_t sInterfacesSize = mozilla::ArrayLength(sInterfaces);

} // namespace detail
} // namespace xpt
"""
    )


def link_and_write(files, outfile, outheader):
    interfaces = []
    for file in files:
        with open(file, "r") as fd:
            interfaces += json.load(fd)

    iids = set()
    names = set()
    for interface in interfaces:
        assert interface["uuid"] not in iids, "duplicated UUID %s" % interface["uuid"]
        assert interface["name"] not in names, "duplicated name %s" % interface["name"]
        iids.add(interface["uuid"])
        names.add(interface["name"])

    # All forwards referenced from scriptable members must be known (as scriptable).
    for iface in interfaces:
        for ref in iface["needs_scriptable"]:
            if not ref in names:
                raise Exception(
                    f"Scriptable member in {iface['name']} references unknown {ref}. "
                    "Forward must be a known and [scriptable] interface, "
                    "or the referencing member marked with [noscript]."
                )

    link_to_cpp(interfaces, outfile, outheader)


def main():
    import sys
    from argparse import ArgumentParser

    parser = ArgumentParser()
    parser.add_argument("outfile", help="Output C++ file to generate")
    parser.add_argument("outheader", help="Output C++ header file to generate")
    parser.add_argument("xpts", nargs="*", help="source xpt files")

    args = parser.parse_args(sys.argv[1:])
    with open(args.outfile, "w") as fd, open(args.outheader, "w") as header_fd:
        link_and_write(args.xpts, fd, header_fd)


if __name__ == "__main__":
    main()