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/*
* Copyright (c) 2021, Matthew Olsson <mattco@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Debug.h>
#include <AK/Function.h>
#include <AK/ScopeGuard.h>
namespace PDF {
class Reader {
public:
explicit Reader(const ReadonlyBytes& bytes)
: m_bytes(bytes)
{
}
ALWAYS_INLINE const ReadonlyBytes& bytes() const { return m_bytes; }
ALWAYS_INLINE size_t offset() const { return m_offset; }
bool done() const
{
if (m_forwards)
return offset() >= bytes().size();
return m_offset < 0;
}
size_t remaining() const
{
if (done())
return 0;
if (m_forwards)
return bytes().size() - offset() - 1;
return offset() + 1;
}
void move_by(size_t count)
{
if (m_forwards) {
m_offset += static_cast<ssize_t>(count);
} else {
m_offset -= static_cast<ssize_t>(count);
}
}
char read()
{
auto value = m_bytes.at(m_offset);
move_by(1);
return static_cast<char>(value);
}
char peek(size_t shift = 0) const
{
auto offset = m_offset + shift * (m_forwards ? 1 : -1);
return static_cast<char>(m_bytes.at(offset));
}
template<typename... T>
bool matches_any(T... elements) const
{
if (done())
return false;
auto ch = peek();
return ((ch == elements) || ...);
}
bool matches(char ch) const
{
return !done() && peek() == ch;
}
bool matches(const char* chars) const
{
String string(chars);
if (remaining() < string.length())
return false;
if (!m_forwards)
string = string.reverse();
for (size_t i = 0; i < string.length(); i++) {
if (peek(i) != string[i])
return false;
}
return true;
}
template<typename T = char>
void move_to(size_t offset)
{
VERIFY(offset < m_bytes.size());
m_offset = static_cast<ssize_t>(offset);
}
void move_until(char ch)
{
while (!done() && peek() != ch)
move_by(1);
}
void move_until(Function<bool(char)> predicate)
{
while (!done() && !predicate(peek()))
move_by(1);
}
ALWAYS_INLINE void move_while(Function<bool(char)> predicate)
{
move_until([&predicate](char t) { return !predicate(t); });
}
ALWAYS_INLINE void set_reading_forwards() { m_forwards = true; }
ALWAYS_INLINE void set_reading_backwards() { m_forwards = false; }
ALWAYS_INLINE void save() { m_saved_offsets.append(m_offset); }
ALWAYS_INLINE void load() { m_offset = m_saved_offsets.take_last(); }
ALWAYS_INLINE void discard() { m_saved_offsets.take_last(); }
#ifdef PDF_DEBUG
void dump_state() const
{
dbgln("Reader State (offset={} size={})", offset(), bytes().size());
size_t from = max(0, static_cast<int>(offset()) - 10);
size_t to = min(bytes().size() - 1, offset() + 10);
for (auto i = from; i <= to; i++) {
char value = static_cast<char>(bytes().at(i));
auto line = String::formatted(" {}: '{}' (value={:3d}) ", i, value, static_cast<u8>(value));
if (i == offset()) {
dbgln("{} <<< current location, forwards={}", line, m_forwards);
} else {
dbgln("{}", line);
}
}
dbgln();
}
#endif
private:
ReadonlyBytes m_bytes;
ssize_t m_offset { 0 };
Vector<ssize_t> m_saved_offsets;
bool m_forwards { true };
};
}
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