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llvm-mirror/lib/Support/FormatVariadic.cpp
Benjamin Kramer b25315e825 [FormatVariadic] Reduce allocations
- Move Adapters array to the stack, we know the size precisely
- Parse format string on demand into a SmallVector. In theory this could
  lead to parsing it multiple times, but I couldn't find a single instance
  of that in LLVM.
- Make more of the implementation details private.
2020-04-11 14:54:32 +02:00

157 lines
5.2 KiB
C++

//===- FormatVariadic.cpp - Format string parsing and analysis ----*-C++-*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//===----------------------------------------------------------------------===//
#include "llvm/Support/FormatVariadic.h"
#include <cassert>
using namespace llvm;
static Optional<AlignStyle> translateLocChar(char C) {
switch (C) {
case '-':
return AlignStyle::Left;
case '=':
return AlignStyle::Center;
case '+':
return AlignStyle::Right;
default:
return None;
}
LLVM_BUILTIN_UNREACHABLE;
}
bool formatv_object_base::consumeFieldLayout(StringRef &Spec, AlignStyle &Where,
size_t &Align, char &Pad) {
Where = AlignStyle::Right;
Align = 0;
Pad = ' ';
if (Spec.empty())
return true;
if (Spec.size() > 1) {
// A maximum of 2 characters at the beginning can be used for something
// other
// than the width.
// If Spec[1] is a loc char, then Spec[0] is a pad char and Spec[2:...]
// contains the width.
// Otherwise, if Spec[0] is a loc char, then Spec[1:...] contains the width.
// Otherwise, Spec[0:...] contains the width.
if (auto Loc = translateLocChar(Spec[1])) {
Pad = Spec[0];
Where = *Loc;
Spec = Spec.drop_front(2);
} else if (auto Loc = translateLocChar(Spec[0])) {
Where = *Loc;
Spec = Spec.drop_front(1);
}
}
bool Failed = Spec.consumeInteger(0, Align);
return !Failed;
}
Optional<ReplacementItem>
formatv_object_base::parseReplacementItem(StringRef Spec) {
StringRef RepString = Spec.trim("{}");
// If the replacement sequence does not start with a non-negative integer,
// this is an error.
char Pad = ' ';
std::size_t Align = 0;
AlignStyle Where = AlignStyle::Right;
StringRef Options;
size_t Index = 0;
RepString = RepString.trim();
if (RepString.consumeInteger(0, Index)) {
assert(false && "Invalid replacement sequence index!");
return ReplacementItem{};
}
RepString = RepString.trim();
if (!RepString.empty() && RepString.front() == ',') {
RepString = RepString.drop_front();
if (!consumeFieldLayout(RepString, Where, Align, Pad))
assert(false && "Invalid replacement field layout specification!");
}
RepString = RepString.trim();
if (!RepString.empty() && RepString.front() == ':') {
Options = RepString.drop_front().trim();
RepString = StringRef();
}
RepString = RepString.trim();
if (!RepString.empty()) {
assert(false && "Unexpected characters found in replacement string!");
}
return ReplacementItem{Spec, Index, Align, Where, Pad, Options};
}
std::pair<ReplacementItem, StringRef>
formatv_object_base::splitLiteralAndReplacement(StringRef Fmt) {
std::size_t From = 0;
while (From < Fmt.size() && From != StringRef::npos) {
std::size_t BO = Fmt.find_first_of('{', From);
// Everything up until the first brace is a literal.
if (BO != 0)
return std::make_pair(ReplacementItem{Fmt.substr(0, BO)}, Fmt.substr(BO));
StringRef Braces =
Fmt.drop_front(BO).take_while([](char C) { return C == '{'; });
// If there is more than one brace, then some of them are escaped. Treat
// these as replacements.
if (Braces.size() > 1) {
size_t NumEscapedBraces = Braces.size() / 2;
StringRef Middle = Fmt.substr(BO, NumEscapedBraces);
StringRef Right = Fmt.drop_front(BO + NumEscapedBraces * 2);
return std::make_pair(ReplacementItem{Middle}, Right);
}
// An unterminated open brace is undefined. We treat the rest of the string
// as a literal replacement, but we assert to indicate that this is
// undefined and that we consider it an error.
std::size_t BC = Fmt.find_first_of('}', BO);
if (BC == StringRef::npos) {
assert(
false &&
"Unterminated brace sequence. Escape with {{ for a literal brace.");
return std::make_pair(ReplacementItem{Fmt}, StringRef());
}
// Even if there is a closing brace, if there is another open brace before
// this closing brace, treat this portion as literal, and try again with the
// next one.
std::size_t BO2 = Fmt.find_first_of('{', BO + 1);
if (BO2 < BC)
return std::make_pair(ReplacementItem{Fmt.substr(0, BO2)},
Fmt.substr(BO2));
StringRef Spec = Fmt.slice(BO + 1, BC);
StringRef Right = Fmt.substr(BC + 1);
auto RI = parseReplacementItem(Spec);
if (RI.hasValue())
return std::make_pair(*RI, Right);
// If there was an error parsing the replacement item, treat it as an
// invalid replacement spec, and just continue.
From = BC + 1;
}
return std::make_pair(ReplacementItem{Fmt}, StringRef());
}
SmallVector<ReplacementItem, 2>
formatv_object_base::parseFormatString(StringRef Fmt) {
SmallVector<ReplacementItem, 2> Replacements;
ReplacementItem I;
while (!Fmt.empty()) {
std::tie(I, Fmt) = splitLiteralAndReplacement(Fmt);
if (I.Type != ReplacementType::Empty)
Replacements.push_back(I);
}
return Replacements;
}
void detail::format_adapter::anchor() { }