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LibPDF: Extract reference bitpacking into dedicated class

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This commit is contained in:
Ben Wiederhake 2021-09-18 17:15:14 +02:00 committed by Ali Mohammad Pur
parent da170997d5
commit d344253b08
3 changed files with 52 additions and 16 deletions
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2
Userland/Libraries/LibPDF/Parser.cpp
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@ -660,7 +660,7 @@ Value Parser::parse_possible_indirect_value_or_ref()
m_reader.discard();
consume();
consume_whitespace();
return Value(first_number.as_int(), second_number.as_int());
return Value(Reference(first_number.as_int(), second_number.as_int()));
}
if (m_reader.matches("obj")) {

45
Userland/Libraries/LibPDF/Reference.h Normal file
View file

@ -0,0 +1,45 @@
/*
* Copyright (c) 2021, Matthew Olsson <mattco@serenityos.org>
* Copyright (c) 2021, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Types.h>
namespace PDF {
class Reference {
// We store refs as u32, with 18 bits for the index and 14 bits for the
// generation index. The generation index is stored in the higher bits.
// This may need to be rethought later, as the max generation index is
// 2^16 and the max for the object index is probably 2^32 (I don't know
// exactly)
static constexpr auto MAX_REF_INDEX = (1 << 19) - 1; // 2 ^ 19 - 1
static constexpr auto MAX_REF_GENERATION_INDEX = (1 << 15) - 1; // 2 ^ 15 - 1
public:
Reference(u32 index, u32 generation_index)
{
VERIFY(index < MAX_REF_INDEX);
VERIFY(generation_index < MAX_REF_GENERATION_INDEX);
m_combined = (generation_index << 14) | index;
}
[[nodiscard]] ALWAYS_INLINE u32 as_ref_index() const
{
return m_combined & 0x3ffff;
}
[[nodiscard]] ALWAYS_INLINE u32 as_ref_generation_index() const
{
return m_combined >> 18;
}
private:
u32 m_combined;
};
}

21
Userland/Libraries/LibPDF/Value.h
View file

@ -11,19 +11,12 @@
#include <AK/String.h>
#include <LibPDF/Forward.h>
#include <LibPDF/Object.h>
#include <LibPDF/Reference.h>
namespace PDF {
class Value {
public:
// We store refs as u32, with 18 bits for the index and 14 bits for the
// generation index. The generation index is stored in the higher bits.
// This may need to be rethought later, as the max generation index is
// 2^16 and the max for the object index is probably 2^32 (I don't know
// exactly)
static constexpr auto max_ref_index = (1 << 19) - 1; // 2 ^ 19 - 1
static constexpr auto max_ref_generation_index = (1 << 15) - 1; // 2 ^ 15 - 1
Value()
: m_type(Type::Empty)
{
@ -55,12 +48,10 @@ public:
m_as_float = f;
}
Value(u32 index, u32 generation_index)
Value(Reference ref)
: m_type(Type::Ref)
{
VERIFY(index < max_ref_index);
VERIFY(generation_index < max_ref_generation_index);
m_as_ref = (generation_index << 14) | index;
m_as_ref = ref;
}
template<IsObject T>
@ -148,13 +139,13 @@ public:
[[nodiscard]] ALWAYS_INLINE u32 as_ref_index() const
{
VERIFY(is_ref());
return m_as_ref & 0x3ffff;
return m_as_ref.as_ref_index();
}
[[nodiscard]] ALWAYS_INLINE u32 as_ref_generation_index() const
{
VERIFY(is_ref());
return m_as_ref >> 18;
return m_as_ref.as_ref_generation_index();
}
[[nodiscard]] ALWAYS_INLINE NonnullRefPtr<Object> as_object() const { return *m_as_object; }
@ -177,7 +168,7 @@ private:
union {
bool m_as_bool;
int m_as_int;
u32 m_as_ref;
Reference m_as_ref;
float m_as_float;
};