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fs: reduce path size 0x28 -> 0x18

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This implements two optimizations on fs::Path, which N added in 12.0.0.

The current structure looks like: 

```cpp
struct Path {
    const char *m_str; // Points to the read-only path string
    char *m_write_buffer_buffer; // Part of std::unique_ptr<char[], ams::fs::impl::Deleter>
    ams::fs::impl::Deleter m_write_buffer_deleter; // Parse of std::unique_ptr<char[], ams::fs::impl::Deleter>, stores the size of the buffer.
    size_t m_write_buffer_length; // Copy of the write buffer's size accessible to the Path() structure.
    bool m_is_normalized; // Whether the path buffer is normalized
};
```

This is pretty wasteful. The write buffer size is stored twice, wasting 8 bytes, because one copy of the size isn't accessible to the path.

In addition, due to alignment, the bool wastes 7 padding bytes.

This commit:

* Encodes normalized in the low bit of the write buffer length, saving 8 bytes.
* Use a custom WriteBuffer class rather than generic unique_ptr, to avoid needing to store the WriteBuffer twice.


These each save 8 bytes, for a final size of 0x18 rather than 0x28.
This commit is contained in:
SciresM 2022-03-24 20:22:47 -07:00 committed by GitHub
parent 817ad8f98d
commit 64c6ef2de7
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 172 additions and 84 deletions
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17
libraries/libstratosphere/include/stratosphere/fs/fs_memory_management.hpp
View file

@ -26,6 +26,8 @@ namespace ams::fs {
namespace impl {
class Newable;
void *Allocate(size_t size);
void Deallocate(void *ptr, size_t size);
@ -130,20 +132,27 @@ namespace ams::fs {
};
template<typename T>
std::unique_ptr<T, Deleter> MakeUnique() {
static_assert(util::is_pod<T>::value);
auto MakeUnique() {
/* Check that we're not using MakeUnique unnecessarily. */
static_assert(!std::derived_from<T, ::ams::fs::impl::Newable>);
return std::unique_ptr<T, Deleter>(static_cast<T *>(::ams::fs::impl::Allocate(sizeof(T))), Deleter(sizeof(T)));
}
template<typename ArrayT>
std::unique_ptr<ArrayT, Deleter> MakeUnique(size_t size) {
auto MakeUnique(size_t size) {
using T = typename std::remove_extent<ArrayT>::type;
static_assert(util::is_pod<ArrayT>::value);
static_assert(std::is_array<ArrayT>::value);
/* Check that we're not using MakeUnique unnecessarily. */
static_assert(!std::derived_from<T, ::ams::fs::impl::Newable>);
using ReturnType = std::unique_ptr<ArrayT, Deleter>;
const size_t alloc_size = sizeof(T) * size;
return std::unique_ptr<ArrayT, Deleter>(static_cast<T *>(::ams::fs::impl::Allocate(alloc_size)), Deleter(alloc_size));
return ReturnType(static_cast<T *>(::ams::fs::impl::Allocate(alloc_size)), Deleter(alloc_size));
}
}

239
libraries/libstratosphere/include/stratosphere/fs/fs_path.hpp
View file

@ -24,6 +24,7 @@ namespace ams::fs {
class DirectoryPathParser;
/* ACCURATE_TO_VERSION: 13.4.0.0 */
/* NOTE: Intentional inaccuracy in custom WriteBuffer class, to save 0x10 bytes (0x28 -> 0x18) over Nintendo's implementation. */
class Path {
NON_COPYABLE(Path);
NON_MOVEABLE(Path);
@ -32,43 +33,111 @@ namespace ams::fs {
static constexpr size_t WriteBufferAlignmentLength = 8;
private:
friend class DirectoryPathParser;
private:
using WriteBuffer = std::unique_ptr<char[], ::ams::fs::impl::Deleter>;
public:
class WriteBuffer {
NON_COPYABLE(WriteBuffer);
private:
char *m_buffer;
size_t m_length_and_is_normalized;
public:
constexpr WriteBuffer() : m_buffer(nullptr), m_length_and_is_normalized(0) { /* ... */ }
constexpr ~WriteBuffer() {
if (m_buffer != nullptr) {
::ams::fs::impl::Deallocate(m_buffer, this->GetLength());
this->ResetBuffer();
}
}
constexpr WriteBuffer(WriteBuffer &&rhs) : m_buffer(rhs.m_buffer), m_length_and_is_normalized(rhs.m_length_and_is_normalized) {
rhs.ResetBuffer();
}
constexpr WriteBuffer &operator=(WriteBuffer &&rhs) {
m_buffer = rhs.m_buffer;
m_length_and_is_normalized = rhs.m_length_and_is_normalized;
rhs.ResetBuffer();
return *this;
}
std::unique_ptr<char[], ::ams::fs::impl::Deleter> ReleaseBuffer() {
auto released = std::unique_ptr<char[], ::ams::fs::impl::Deleter>(m_buffer, ::ams::fs::impl::Deleter(this->GetLength()));
this->ResetBuffer();
return released;
}
constexpr ALWAYS_INLINE void ResetBuffer() {
m_buffer = nullptr;
this->SetLength(0);
}
constexpr ALWAYS_INLINE char *Get() const {
return m_buffer;
}
constexpr ALWAYS_INLINE size_t GetLength() const {
return m_length_and_is_normalized >> 1;
}
constexpr ALWAYS_INLINE bool IsNormalized() const {
return static_cast<bool>(m_length_and_is_normalized & 1);
}
constexpr ALWAYS_INLINE void SetNormalized() {
m_length_and_is_normalized |= static_cast<size_t>(1);
}
constexpr ALWAYS_INLINE void SetNotNormalized() {
m_length_and_is_normalized &= ~static_cast<size_t>(1);
}
private:
constexpr ALWAYS_INLINE WriteBuffer(char *buffer, size_t length) : m_buffer(buffer), m_length_and_is_normalized(0) {
this->SetLength(length);
}
public:
static WriteBuffer Make(size_t length) {
if (void *alloc = ::ams::fs::impl::Allocate(length); alloc != nullptr) {
return WriteBuffer(static_cast<char *>(alloc), length);
} else {
return WriteBuffer();
}
}
private:
constexpr ALWAYS_INLINE void SetLength(size_t size) {
m_length_and_is_normalized = (m_length_and_is_normalized & 1) | (size << 1);
}
};
private:
const char *m_str;
util::TypedStorage<WriteBuffer> m_write_buffer;
size_t m_write_buffer_length;
bool m_is_normalized;
WriteBuffer m_write_buffer;
public:
Path() : m_str(EmptyPath), m_write_buffer_length(0), m_is_normalized(false) {
util::ConstructAt(m_write_buffer, nullptr);
}
constexpr Path(const char *s, util::ConstantInitializeTag) : m_str(s), m_write_buffer(), m_write_buffer_length(0), m_is_normalized(true) {
constexpr Path() : m_str(EmptyPath), m_write_buffer() {
/* ... */
}
constexpr ~Path() {
if (!std::is_constant_evaluated()) {
util::DestroyAt(m_write_buffer);
}
constexpr Path(const char *s, util::ConstantInitializeTag) : m_str(s), m_write_buffer() {
m_write_buffer.SetNormalized();
}
WriteBuffer ReleaseBuffer() {
constexpr ~Path() { /* ... */ }
std::unique_ptr<char[], ::ams::fs::impl::Deleter> ReleaseBuffer() {
/* Check pre-conditions. */
AMS_ASSERT(util::GetReference(m_write_buffer) != nullptr);
AMS_ASSERT(m_write_buffer.Get() != nullptr);
/* Reset. */
m_str = EmptyPath;
m_write_buffer_length = 0;
m_str = EmptyPath;
/* Return our write buffer. */
return std::move(util::GetReference(m_write_buffer));
/* Release our write buffer. */
return m_write_buffer.ReleaseBuffer();
}
constexpr Result SetShallowBuffer(const char *buffer) {
/* Check pre-conditions. */
AMS_ASSERT(m_write_buffer_length == 0);
AMS_ASSERT(m_write_buffer.GetLength() == 0);
/* Check the buffer is valid. */
R_UNLESS(buffer != nullptr, fs::ResultNullptrArgument());
@ -77,14 +146,14 @@ namespace ams::fs {
this->SetReadOnlyBuffer(buffer);
/* Note that we're normalized. */
m_is_normalized = true;
this->SetNormalized();
R_SUCCEED();
}
const char *GetString() const {
/* Check pre-conditions. */
AMS_ASSERT(m_is_normalized);
AMS_ASSERT(this->IsNormalized());
return m_str;
}
@ -103,18 +172,19 @@ namespace ams::fs {
Result Initialize(const Path &rhs) {
/* Check the other path is normalized. */
R_UNLESS(rhs.m_is_normalized, fs::ResultNotNormalized());
const bool normalized = rhs.IsNormalized();
R_UNLESS(normalized, fs::ResultNotNormalized());
/* Allocate buffer for our path. */
const auto len = rhs.GetLength();
R_TRY(this->Preallocate(len + 1));
/* Copy the path. */
const size_t copied = util::Strlcpy<char>(util::GetReference(m_write_buffer).get(), rhs.GetString(), len + 1);
const size_t copied = util::Strlcpy<char>(m_write_buffer.Get(), rhs.GetString(), len + 1);
R_UNLESS(copied == len, fs::ResultUnexpectedInPathA());
/* Set normalized. */
m_is_normalized = rhs.m_is_normalized;
this->SetNormalized();
R_SUCCEED();
}
@ -126,7 +196,7 @@ namespace ams::fs {
R_TRY(this->InitializeImpl(path, len));
/* Set not normalized. */
m_is_normalized = false;
this->SetNotNormalized();
R_SUCCEED();
}
@ -154,7 +224,7 @@ namespace ams::fs {
R_TRY(this->Preallocate(len + 1));
/* Format our path into our new buffer. */
const auto real_len = util::VSNPrintf(util::GetReference(m_write_buffer).get(), m_write_buffer_length, fmt, vl);
const auto real_len = util::VSNPrintf(m_write_buffer.Get(), m_write_buffer.GetLength(), fmt, vl);
AMS_ASSERT(real_len == len);
AMS_UNUSED(real_len);
@ -162,7 +232,7 @@ namespace ams::fs {
va_end(vl);
/* Set not normalized. */
m_is_normalized = false;
this->SetNotNormalized();
R_SUCCEED();
}
@ -175,12 +245,12 @@ namespace ams::fs {
R_TRY(this->InitializeImpl(path, std::strlen(path)));
/* Replace slashes as desired. */
if (m_write_buffer_length > 1) {
fs::Replace(this->GetWriteBuffer(), m_write_buffer_length - 1, '\\', '/');
if (const auto write_buffer_length = m_write_buffer.GetLength(); write_buffer_length > 1) {
fs::Replace(m_write_buffer.Get(), write_buffer_length - 1, '\\', '/');
}
/* Set not normalized. */
m_is_normalized = false;
this->SetNotNormalized();
R_SUCCEED();
}
@ -193,15 +263,15 @@ namespace ams::fs {
R_TRY(this->InitializeImpl(path, std::strlen(path)));
/* Replace slashes as desired. */
if (m_write_buffer_length > 1) {
if (auto *p = this->GetWriteBuffer(); p[0] == '/' && p[1] == '/') {
if (m_write_buffer.GetLength() > 1) {
if (auto *p = m_write_buffer.Get(); p[0] == '/' && p[1] == '/') {
p[0] = '\\';
p[1] = '\\';
}
}
/* Set not normalized. */
m_is_normalized = false;
this->SetNotNormalized();
R_SUCCEED();
}
@ -214,11 +284,11 @@ namespace ams::fs {
R_TRY(this->InitializeImpl(path, std::strlen(path)));
/* Set not normalized. */
m_is_normalized = false;
this->SetNotNormalized();
/* Replace unc as desired. */
if (m_str[0]) {
auto *p = this->GetWriteBuffer();
auto *p = m_write_buffer.Get();
/* Replace :/// -> \\ as needed. */
if (auto *sep = std::strstr(p, ":///"); sep != nullptr) {
@ -251,7 +321,7 @@ namespace ams::fs {
R_TRY(this->InitializeImpl(path, size));
/* Set not normalized. */
m_is_normalized = false;
this->SetNotNormalized();
/* Perform normalization. */
fs::PathFlags path_flags;
@ -263,16 +333,17 @@ namespace ams::fs {
/* NOTE: In this case, Nintendo checks is normalized, then sets is normalized, then returns success. */
/* This seems like a bug. */
size_t dummy;
R_TRY(PathFormatter::IsNormalized(std::addressof(m_is_normalized), std::addressof(dummy), m_str));
bool normalized;
R_TRY(PathFormatter::IsNormalized(std::addressof(normalized), std::addressof(dummy), m_str));
m_is_normalized = true;
this->SetNormalized();
R_SUCCEED();
}
/* Normalize. */
R_TRY(this->Normalize(path_flags));
m_is_normalized = true;
this->SetNormalized();
R_SUCCEED();
}
@ -288,7 +359,7 @@ namespace ams::fs {
this->ClearBuffer();
/* Set normalized. */
m_is_normalized = true;
this->SetNormalized();
R_SUCCEED();
}
@ -324,8 +395,8 @@ namespace ams::fs {
/* Reset our write buffer. */
WriteBuffer old_write_buffer;
if (util::GetReference(m_write_buffer) != nullptr) {
old_write_buffer = std::move(util::GetReference(m_write_buffer));
if (m_write_buffer.Get() != nullptr) {
old_write_buffer = std::move(m_write_buffer);
this->ClearBuffer();
}
@ -333,9 +404,9 @@ namespace ams::fs {
R_TRY(this->Preallocate(cur_len + 1 + child_len + 1));
/* Get our write buffer. */
auto *dst = this->GetWriteBuffer();
if (old_write_buffer != nullptr && cur_len > 0) {
util::Strlcpy<char>(dst, old_write_buffer.get(), cur_len + 1);
auto *dst = m_write_buffer.Get();
if (old_write_buffer.Get() != nullptr && cur_len > 0) {
util::Strlcpy<char>(dst, old_write_buffer.Get(), cur_len + 1);
}
/* Add separator. */
@ -376,15 +447,15 @@ namespace ams::fs {
Result RemoveChild() {
/* If we don't have a write-buffer, ensure that we have one. */
if (util::GetReference(m_write_buffer) == nullptr) {
if (m_write_buffer.Get() == nullptr) {
if (const auto len = std::strlen(m_str); len > 0) {
R_TRY(this->Preallocate(len));
util::Strlcpy<char>(util::GetReference(m_write_buffer).get(), m_str, len + 1);
util::Strlcpy<char>(m_write_buffer.Get(), m_str, len + 1);
}
}
/* Check that it's possible for us to remove a child. */
auto *p = this->GetWriteBuffer();
auto *p = m_write_buffer.Get();
s32 len = std::strlen(p);
R_UNLESS(len != 1 || (p[0] != '/' && p[0] != '.'), fs::ResultNotImplemented());
@ -414,7 +485,7 @@ namespace ams::fs {
Result Normalize(const PathFlags &flags) {
/* If we're already normalized, nothing to do. */
R_SUCCEED_IF(m_is_normalized);
R_SUCCEED_IF(this->IsNormalized());
/* Check if we're normalized. */
bool normalized;
@ -424,7 +495,7 @@ namespace ams::fs {
/* If we're not normalized, normalize. */
if (!normalized) {
/* Determine necessary buffer length. */
auto len = m_write_buffer_length;
auto len = m_write_buffer.GetLength();
if (flags.IsRelativePathAllowed() && fs::IsPathRelative(m_str)) {
len += 2;
}
@ -434,57 +505,59 @@ namespace ams::fs {
/* Allocate a new buffer. */
const size_t size = util::AlignUp(len, WriteBufferAlignmentLength);
auto buf = fs::impl::MakeUnique<char[]>(size);
R_UNLESS(buf != nullptr, fs::ResultAllocationMemoryFailedMakeUnique());
auto buf = WriteBuffer::Make(size);
R_UNLESS(buf.Get() != nullptr, fs::ResultAllocationMemoryFailedMakeUnique());
/* Normalize into it. */
R_TRY(PathFormatter::Normalize(buf.get(), size, util::GetReference(m_write_buffer).get(), m_write_buffer_length, flags));
R_TRY(PathFormatter::Normalize(buf.Get(), size, m_write_buffer.Get(), m_write_buffer.GetLength(), flags));
/* Set the normalized buffer as our buffer. */
this->SetModifiableBuffer(std::move(buf), size);
this->SetModifiableBuffer(std::move(buf));
}
/* Set normalized. */
m_is_normalized = true;
this->SetNormalized();
R_SUCCEED();
}
private:
void ClearBuffer() {
util::GetReference(m_write_buffer).reset();
m_write_buffer_length = 0;
m_write_buffer.ResetBuffer();
m_str = EmptyPath;
}
void SetModifiableBuffer(WriteBuffer &&buffer, size_t size) {
void SetModifiableBuffer(WriteBuffer &&buffer) {
/* Check pre-conditions. */
AMS_ASSERT(buffer.get() != nullptr);
AMS_ASSERT(size > 0);
AMS_ASSERT(util::IsAligned(size, WriteBufferAlignmentLength));
AMS_ASSERT(buffer.Get() != nullptr);
AMS_ASSERT(buffer.GetLength() > 0);
AMS_ASSERT(util::IsAligned(buffer.GetLength(), WriteBufferAlignmentLength));
/* Get whether we're normalized. */
if (m_write_buffer.IsNormalized()) {
buffer.SetNormalized();
} else {
buffer.SetNotNormalized();
}
/* Set write buffer. */
util::GetReference(m_write_buffer) = std::move(buffer);
m_write_buffer_length = size;
m_str = util::GetReference(m_write_buffer).get();
m_write_buffer = std::move(buffer);
m_str = m_write_buffer.Get();
}
constexpr void SetReadOnlyBuffer(const char *buffer) {
m_str = buffer;
if (!std::is_constant_evaluated()) {
util::GetReference(m_write_buffer) = nullptr;
m_write_buffer_length = 0;
}
m_write_buffer.ResetBuffer();
}
Result Preallocate(size_t length) {
/* Allocate additional space, if needed. */
if (length > m_write_buffer_length) {
if (length > m_write_buffer.GetLength()) {
/* Allocate buffer. */
const size_t size = util::AlignUp(length, WriteBufferAlignmentLength);
auto buf = fs::impl::MakeUnique<char[]>(size);
R_UNLESS(buf != nullptr, fs::ResultAllocationMemoryFailedMakeUnique());
auto buf = WriteBuffer::Make(size);
R_UNLESS(buf.Get() != nullptr, fs::ResultAllocationMemoryFailedMakeUnique());
/* Set write buffer. */
this->SetModifiableBuffer(std::move(buf), size);
this->SetModifiableBuffer(std::move(buf));
}
R_SUCCEED();
@ -496,7 +569,7 @@ namespace ams::fs {
R_TRY(this->Preallocate(size + 1));
/* Copy the path. */
const size_t copied = util::Strlcpy<char>(this->GetWriteBuffer(), path, size + 1);
const size_t copied = util::Strlcpy<char>(m_write_buffer.Get(), path, size + 1);
R_UNLESS(copied >= size, fs::ResultUnexpectedInPathA());
} else {
/* We can just clear the buffer. */
@ -506,14 +579,20 @@ namespace ams::fs {
R_SUCCEED();
}
char *GetWriteBuffer() {
AMS_ASSERT(util::GetReference(m_write_buffer) != nullptr);
return util::GetReference(m_write_buffer).get();
constexpr char *GetWriteBuffer() {
AMS_ASSERT(m_write_buffer.Get() != nullptr);
return m_write_buffer.Get();
}
size_t GetWriteBufferLength() const {
return m_write_buffer_length;
constexpr ALWAYS_INLINE size_t GetWriteBufferLength() const {
return m_write_buffer.GetLength();
}
constexpr ALWAYS_INLINE bool IsNormalized() const { return m_write_buffer.IsNormalized(); }
constexpr ALWAYS_INLINE void SetNormalized() { m_write_buffer.SetNormalized(); }
constexpr ALWAYS_INLINE void SetNotNormalized() { m_write_buffer.SetNotNormalized(); }
public:
ALWAYS_INLINE bool operator==(const fs::Path &rhs) const { return std::strcmp(this->GetString(), rhs.GetString()) == 0; }
ALWAYS_INLINE bool operator!=(const fs::Path &rhs) const { return !(*this == rhs); }