forked from mirrors/gecko-dev
265 lines
9.1 KiB
Python
265 lines
9.1 KiB
Python
# -*- coding: utf-8 -*-
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# This Source Code Form is subject to the terms of the Mozilla Public
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# License, v. 2.0. If a copy of the MPL was not distributed with this
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# file, You can obtain one at http://mozilla.org/MPL/2.0/.
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"""
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Outputter to generate C++ code for the JavaScript API for metrics.
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The code for the JavaScript API is a bit special in that we only generate C++ code,
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string tables and mapping functions.
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The rest is handled by the WebIDL and XPIDL implementation
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that uses this code to look up metrics by name.
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"""
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import jinja2
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from perfecthash import PerfectHash
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from string_table import StringTable
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from util import generate_metric_ids, generate_ping_ids
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from glean_parser import util
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"""
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We need to store several bits of information in the Perfect Hash Map Entry:
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1. An index into the string table to check for string equality with a search key
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The perfect hash function will give false-positive for non-existent keys,
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so we need to verify these ourselves.
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2. Type information to instantiate the correct C++ class
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3. The metric's actual ID to lookup the underlying instance.
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We have 64 bits to play with, so we dedicate:
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1. 32 bit to the string table offset. More than enough for a large string table (~60M metrics).
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2. 5 bit for the type. That allows for 32 metric types. We're not even close to that yet.
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3. 27 bit for the metric ID. That allows for 130 million metrics. Let's not go there.
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These values are interpolated into the template as well, so changing them here
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ensures the generated C++ code follows.
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If we ever need more bits for a part (e.g. when we add the 33rd metric type),
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we figure out if either the string table indices or the range of possible IDs can be reduced
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and adjust the constants below.
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"""
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ENTRY_WIDTH = 64
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INDEX_BITS = 32
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ID_BITS = 27
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PING_INDEX_BITS = 16
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def ping_entry(ping_id, ping_string_index):
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"""
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The 2 pieces of information of a ping encoded into a single 32-bit integer.
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"""
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assert ping_id < 2 ** (32 - PING_INDEX_BITS)
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assert ping_string_index < 2 ** PING_INDEX_BITS
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return ping_id << PING_INDEX_BITS | ping_string_index
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def create_entry(metric_id, type_id, idx):
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"""
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The 3 pieces of information of a metric encoded into a single 64-bit integer.
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"""
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return metric_id << INDEX_BITS | type_id << (INDEX_BITS + ID_BITS) | idx
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def metric_identifier(category, metric_name):
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"""
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The metric's unique identifier, including the category and name
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"""
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return f"{category}.{util.camelize(metric_name)}"
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def type_name(obj):
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"""
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Returns the C++ type to use for a given metric object.
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"""
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if getattr(obj, "labeled", False):
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return "GleanLabeled"
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return "Glean" + util.Camelize(obj.type)
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def subtype_name(obj):
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"""
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Returns the subtype name for labeled metrics.
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(e.g. 'boolean' for 'labeled_boolean').
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Returns "" for non-labeled metrics.
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"""
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if getattr(obj, "labeled", False):
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type = obj.type[8:] # strips "labeled_" off the front
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return "Glean" + util.Camelize(type)
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return ""
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def output_js(objs, output_fd, options={}):
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"""
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Given a tree of objects, output code for the JS API to the file-like object `output_fd`.
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:param objs: A tree of objects (metrics and pings) as returned from
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`parser.parse_objects`.
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:param output_fd: Writeable file to write the output to.
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:param options: options dictionary.
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"""
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# Monkeypatch util.get_jinja2_template to find templates nearby
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def get_local_template(template_name, filters=()):
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env = jinja2.Environment(
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loader=jinja2.PackageLoader("js", "templates"),
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trim_blocks=True,
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lstrip_blocks=True,
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)
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env.filters["Camelize"] = util.Camelize
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for filter_name, filter_func in filters:
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env.filters[filter_name] = filter_func
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return env.get_template(template_name)
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util.get_jinja2_template = get_local_template
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if len(objs) == 1 and "pings" in objs:
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write_pings(objs, output_fd, "js_pings.jinja2")
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else:
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write_metrics(objs, output_fd, "js.jinja2")
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def write_metrics(objs, output_fd, template_filename):
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"""
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Given a tree of objects `objs`, output metrics-only code for the JS API to the
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file-like object `output_fd` using template `template_filename`
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"""
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template = util.get_jinja2_template(
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template_filename,
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)
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assert (
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INDEX_BITS + ID_BITS < ENTRY_WIDTH
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), "INDEX_BITS or ID_BITS are larger than allowed"
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get_metric_id = generate_metric_ids(objs)
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# Mapping from a metric's identifier to the entry (metric ID | type id | index)
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metric_id_mapping = {}
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categories = []
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category_string_table = StringTable()
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metric_string_table = StringTable()
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# Mapping from a type name to its ID
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metric_type_ids = {}
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for category_name, objs in objs.items():
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category_name = util.camelize(category_name)
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id = category_string_table.stringIndex(category_name)
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categories.append((category_name, id))
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for metric in objs.values():
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identifier = metric_identifier(category_name, metric.name)
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metric_type_tuple = (type_name(metric), subtype_name(metric))
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if metric_type_tuple in metric_type_ids:
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type_id, _ = metric_type_ids[metric_type_tuple]
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else:
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type_id = len(metric_type_ids) + 1
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metric_type_ids[metric_type_tuple] = (type_id, metric.type)
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idx = metric_string_table.stringIndex(identifier)
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metric_id = get_metric_id(metric)
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entry = create_entry(metric_id, type_id, idx)
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metric_id_mapping[identifier] = entry
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# Create a lookup table for the metric categories only
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category_string_table = category_string_table.writeToString("gCategoryStringTable")
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category_map = [(bytearray(category, "ascii"), id) for (category, id) in categories]
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name_phf = PerfectHash(category_map, 64)
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category_by_name_lookup = name_phf.cxx_codegen(
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name="CategoryByNameLookup",
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entry_type="category_entry_t",
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lower_entry=lambda x: str(x[1]),
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key_type="const nsACString&",
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key_bytes="aKey.BeginReading()",
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key_length="aKey.Length()",
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return_type="static Maybe<uint32_t>",
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return_entry="return category_result_check(aKey, entry);",
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)
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# Create a lookup table for metric's identifiers.
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metric_string_table = metric_string_table.writeToString("gMetricStringTable")
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metric_map = [
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(bytearray(metric_name, "ascii"), metric_id)
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for (metric_name, metric_id) in metric_id_mapping.items()
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]
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metric_phf = PerfectHash(metric_map, 64)
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metric_by_name_lookup = metric_phf.cxx_codegen(
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name="MetricByNameLookup",
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entry_type="metric_entry_t",
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lower_entry=lambda x: str(x[1]),
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key_type="const nsACString&",
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key_bytes="aKey.BeginReading()",
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key_length="aKey.Length()",
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return_type="static Maybe<uint32_t>",
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return_entry="return metric_result_check(aKey, entry);",
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)
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output_fd.write(
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template.render(
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categories=categories,
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metric_id_mapping=metric_id_mapping,
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metric_type_ids=metric_type_ids,
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entry_width=ENTRY_WIDTH,
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index_bits=INDEX_BITS,
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id_bits=ID_BITS,
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category_string_table=category_string_table,
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category_by_name_lookup=category_by_name_lookup,
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metric_string_table=metric_string_table,
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metric_by_name_lookup=metric_by_name_lookup,
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)
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)
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output_fd.write("\n")
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def write_pings(objs, output_fd, template_filename):
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"""
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Given a tree of objects `objs`, output pings-only code for the JS API to the
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file-like object `output_fd` using template `template_filename`
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"""
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template = util.get_jinja2_template(
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template_filename,
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filters=(),
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)
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ping_string_table = StringTable()
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get_ping_id = generate_ping_ids(objs)
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# The map of a ping's name to its entry (a combination of a monotonic
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# integer and its index in the string table)
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pings = {}
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for ping_name in objs["pings"].keys():
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ping_id = get_ping_id(ping_name)
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ping_name = util.camelize(ping_name)
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pings[ping_name] = ping_entry(ping_id, ping_string_table.stringIndex(ping_name))
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ping_map = [
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(bytearray(ping_name, "ascii"), ping_entry)
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for (ping_name, ping_entry) in pings.items()
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]
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ping_string_table = ping_string_table.writeToString("gPingStringTable")
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ping_phf = PerfectHash(ping_map, 64)
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ping_by_name_lookup = ping_phf.cxx_codegen(
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name="PingByNameLookup",
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entry_type="ping_entry_t",
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lower_entry=lambda x: str(x[1]),
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key_type="const nsACString&",
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key_bytes="aKey.BeginReading()",
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key_length="aKey.Length()",
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return_type="static Maybe<uint32_t>",
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return_entry="return ping_result_check(aKey, entry);",
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)
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output_fd.write(
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template.render(
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ping_index_bits=PING_INDEX_BITS,
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ping_by_name_lookup=ping_by_name_lookup,
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ping_string_table=ping_string_table,
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)
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)
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output_fd.write("\n")
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