mirror of
https://github.com/melonDS-emu/melonDS.git
synced 2025-07-23 06:10:03 -06:00
Implement in-memory savestates (#1693)
* Refactor Savestate::Var{8,16,32,64}
- They now delegate to VarArray
- They're declared in the class header so they're likely to be inlined
* First crack at refactoring Savestate to work in-memory
- Well, third, but who's counting?
* Implement Savestate::Finish
* Remove the VersionMajor and VersionMinor fields
- Instead, pull their values directly from the savestate buffer
* Mark a new constructor as explicit
* Rename Reset to Rewind
* Fix a linebreak
* Implement Savestate::Rewind
* Add ROMManager::ClearBackupState
* Refactor ROMManager to use the refactored Savestate
* Capitalize "Least"
- It was driving me nuts
* Add a log call
* Increase default Savestate buffer length to 32MB
* Use C-style file I/O instead of C++-style
- Dumping bytes to a file with C++'s standard library is a MONSTROUS PAIN IN THE ASS
* Quote the savestate's file path for clarity
* Write the savestate's length into the header
* Add some extra logging calls
* Fix section-loading
* Remove the deprecated Savestate constructor
* Convert a char* to a u32 with memcpy, not a cast
* Fix section-handling in loads
* Include <cstring> in Savestate.h
- This was causing a build error on Linux
This commit is contained in:
Jesse Talavera-Greenberg
committed by
GitHub
GitHub
parent
ca7fb4f55e
commit
391ad8c95e
@ -17,12 +17,16 @@
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*/
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#include <stdio.h>
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#include <cassert>
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#include <cstring>
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#include "Savestate.h"
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#include "Platform.h"
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using Platform::Log;
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using Platform::LogLevel;
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static const char* SAVESTATE_MAGIC = "MELN";
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/*
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Savestate format
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@ -46,230 +50,148 @@ using Platform::LogLevel;
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* different minor means adjustments may have to be made
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*/
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// TODO: buffering system! or something of that sort
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// repeated fread/fwrite is slow on Switch
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Savestate::Savestate(const std::string& filename, bool save)
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Savestate::Savestate(void *buffer, u32 size, bool save) :
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Error(false),
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Saving(save),
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CurSection(NO_SECTION),
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buffer(static_cast<u8 *>(buffer)),
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buffer_offset(0),
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buffer_length(size),
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buffer_owned(false),
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finished(false)
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{
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const char* magic = "MELN";
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Error = false;
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if (save)
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if (Saving)
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{
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Saving = true;
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file = Platform::OpenLocalFile(filename, "wb");
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if (!file)
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{
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Log(LogLevel::Error, "savestate: file %s doesn't exist\n", filename.c_str());
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Error = true;
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return;
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}
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VersionMajor = SAVESTATE_MAJOR;
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VersionMinor = SAVESTATE_MINOR;
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fwrite(magic, 4, 1, file);
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fwrite(&VersionMajor, 2, 1, file);
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fwrite(&VersionMinor, 2, 1, file);
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fseek(file, 8, SEEK_CUR); // length to be fixed later
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WriteSavestateHeader();
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}
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else
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{
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Saving = false;
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file = Platform::OpenFile(filename, "rb");
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if (!file)
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// Ensure that the file starts with "MELN"
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u32 read_magic = 0;
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Var32(&read_magic);
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if (read_magic != *((u32*)SAVESTATE_MAGIC))
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{
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Log(LogLevel::Error, "savestate: file %s doesn't exist\n", filename.c_str());
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Log(LogLevel::Error, "savestate: expected magic number %#08x (%s), got %#08x\n",
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*((u32*)SAVESTATE_MAGIC),
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SAVESTATE_MAGIC,
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read_magic
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);
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Error = true;
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return;
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}
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u32 len;
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fseek(file, 0, SEEK_END);
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len = (u32)ftell(file);
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fseek(file, 0, SEEK_SET);
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u32 buf = 0;
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fread(&buf, 4, 1, file);
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if (buf != ((u32*)magic)[0])
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u16 major = 0;
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Var16(&major);
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if (major != SAVESTATE_MAJOR)
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{
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Log(LogLevel::Error, "savestate: invalid magic %08X\n", buf);
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Log(LogLevel::Error, "savestate: bad version major %d, expecting %d\n", major, SAVESTATE_MAJOR);
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Error = true;
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return;
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}
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VersionMajor = 0;
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VersionMinor = 0;
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fread(&VersionMajor, 2, 1, file);
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if (VersionMajor != SAVESTATE_MAJOR)
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u16 minor = 0;
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Var16(&minor);
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if (minor > SAVESTATE_MINOR)
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{
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Log(LogLevel::Error, "savestate: bad version major %d, expecting %d\n", VersionMajor, SAVESTATE_MAJOR);
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Log(LogLevel::Error, "savestate: state from the future, %d > %d\n", minor, SAVESTATE_MINOR);
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Error = true;
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return;
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}
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fread(&VersionMinor, 2, 1, file);
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if (VersionMinor > SAVESTATE_MINOR)
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u32 read_length = 0;
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Var32(&read_length);
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if (read_length != buffer_length)
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{
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Log(LogLevel::Error, "savestate: state from the future, %d > %d\n", VersionMinor, SAVESTATE_MINOR);
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Log(LogLevel::Error, "savestate: expected a length of %d, got %d\n", buffer_length, read_length);
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Error = true;
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return;
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}
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buf = 0;
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fread(&buf, 4, 1, file);
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if (buf != len)
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{
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Log(LogLevel::Error, "savestate: bad length %d\n", buf);
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Error = true;
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return;
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}
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// The next 4 bytes are reserved
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buffer_offset += 4;
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}
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}
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fseek(file, 4, SEEK_CUR);
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Savestate::Savestate(u32 initial_size) :
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Error(false),
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Saving(true), // Can't load from an empty buffer
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CurSection(NO_SECTION),
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buffer(nullptr),
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buffer_offset(0),
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buffer_length(initial_size),
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buffer_owned(true),
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finished(false)
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{
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buffer = static_cast<u8 *>(malloc(buffer_length));
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if (buffer == nullptr)
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{
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Log(LogLevel::Error, "savestate: failed to allocate %d bytes\n", buffer_length);
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Error = true;
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return;
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}
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CurSection = -1;
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WriteSavestateHeader();
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}
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Savestate::~Savestate()
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{
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if (Error) return;
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if (Saving)
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{
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if (CurSection != 0xFFFFFFFF)
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{
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u32 pos = (u32)ftell(file);
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fseek(file, CurSection+4, SEEK_SET);
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u32 len = pos - CurSection;
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fwrite(&len, 4, 1, file);
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fseek(file, pos, SEEK_SET);
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}
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fseek(file, 0, SEEK_END);
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u32 len = (u32)ftell(file);
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fseek(file, 8, SEEK_SET);
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fwrite(&len, 4, 1, file);
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if (Saving && !finished && !buffer_owned && !Error)
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{ // If we haven't finished saving, and there hasn't been an error...
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Finish();
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// No need to close the active section for an owned buffer,
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// it's about to be thrown out.
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}
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if (file) fclose(file);
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if (buffer_owned)
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{
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free(buffer);
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}
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}
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void Savestate::Section(const char* magic)
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{
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if (Error) return;
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if (Error || finished) return;
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if (Saving)
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{
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if (CurSection != 0xFFFFFFFF)
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// Go back to the current section's header and write the length
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CloseCurrentSection();
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CurSection = buffer_offset;
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// Write the new section's magic number
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VarArray((void*)magic, 4);
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// The next 4 bytes are the length, which we'll come back to later.
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u32 zero = 0;
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Var32(&zero);
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// The 8 bytes afterward are reserved, so we skip them.
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Var32(&zero);
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Var32(&zero);
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}
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else
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{
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u32 section_offset = FindSection(magic);
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if (section_offset != NO_SECTION)
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{
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u32 pos = (u32)ftell(file);
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fseek(file, CurSection+4, SEEK_SET);
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u32 len = pos - CurSection;
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fwrite(&len, 4, 1, file);
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fseek(file, pos, SEEK_SET);
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buffer_offset = section_offset;
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}
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CurSection = (u32)ftell(file);
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fwrite(magic, 4, 1, file);
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fseek(file, 12, SEEK_CUR);
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}
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else
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{
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fseek(file, 0x10, SEEK_SET);
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for (;;)
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else
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{
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u32 buf = 0;
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fread(&buf, 4, 1, file);
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if (buf != ((u32*)magic)[0])
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{
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if (buf == 0)
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{
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Log(LogLevel::Error, "savestate: section %s not found. blarg\n", magic);
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return;
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}
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buf = 0;
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fread(&buf, 4, 1, file);
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fseek(file, buf-8, SEEK_CUR);
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continue;
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}
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fseek(file, 12, SEEK_CUR);
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break;
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Log(LogLevel::Error, "savestate: section %s not found. blarg\n", magic);
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Error = true;
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}
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}
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}
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void Savestate::Var8(u8* var)
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{
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if (Error) return;
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if (Saving)
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{
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fwrite(var, 1, 1, file);
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}
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else
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{
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fread(var, 1, 1, file);
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}
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}
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void Savestate::Var16(u16* var)
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{
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if (Error) return;
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if (Saving)
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{
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fwrite(var, 2, 1, file);
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}
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else
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{
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fread(var, 2, 1, file);
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}
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}
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void Savestate::Var32(u32* var)
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{
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if (Error) return;
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if (Saving)
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{
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fwrite(var, 4, 1, file);
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}
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else
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{
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fread(var, 4, 1, file);
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}
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}
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void Savestate::Var64(u64* var)
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{
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if (Error) return;
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if (Saving)
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{
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fwrite(var, 8, 1, file);
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}
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else
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{
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fread(var, 8, 1, file);
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}
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}
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void Savestate::Bool32(bool* var)
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{
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// for compability
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// for compatibility
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if (Saving)
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{
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u32 val = *var;
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@ -285,14 +207,175 @@ void Savestate::Bool32(bool* var)
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void Savestate::VarArray(void* data, u32 len)
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{
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if (Error) return;
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if (Error || finished) return;
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assert(buffer_offset <= buffer_length);
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if (Saving)
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{
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fwrite(data, len, 1, file);
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if (buffer_offset + len > buffer_length)
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{ // If writing the given data would take us past the buffer's end...
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Log(LogLevel::Warn, "savestate: %u-byte write would exceed %u-byte savestate buffer\n", len, buffer_length);
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if (!(buffer_owned && Resize(buffer_length * 2 + len)))
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{ // If we're not allowed to resize this buffer, or if we are but failed...
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Log(LogLevel::Error, "savestate: Failed to write %d bytes to savestate\n", len);
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Error = true;
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return;
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}
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// The buffer's length is doubled, plus however much memory is needed for this write.
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// This way we can write the data and reduce the chance of needing to resize again.
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}
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memcpy(buffer + buffer_offset, data, len);
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}
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else
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{
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fread(data, len, 1, file);
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if (buffer_offset + len > buffer_length)
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{ // If reading the requested amount of data would take us past the buffer's edge...
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Log(LogLevel::Error, "savestate: %u-byte read would exceed %u-byte savestate buffer\n", len, buffer_length);
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Error = true;
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return;
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// Can't realloc here.
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// Not only do we not own the buffer pointer (when loading a state),
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// but we can't magically make the desired data appear.
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}
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memcpy(data, buffer + buffer_offset, len);
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}
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buffer_offset += len;
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}
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void Savestate::Finish()
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{
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if (Error || finished) return;
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CloseCurrentSection();
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WriteStateLength();
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finished = true;
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}
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void Savestate::Rewind(bool save)
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{
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Error = false;
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Saving = save;
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CurSection = NO_SECTION;
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buffer_offset = 0;
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finished = false;
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}
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void Savestate::CloseCurrentSection()
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{
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if (CurSection != NO_SECTION && !finished)
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{ // If we're in the middle of writing a section...
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// Go back to the section's header
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// Get the length of the section we've written thus far
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u32 section_length = buffer_offset - CurSection;
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// Write the length in the section's header
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// (specifically the first 4 bytes after the magic number)
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memcpy(buffer + CurSection + 4, §ion_length, sizeof(section_length));
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CurSection = NO_SECTION;
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}
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}
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bool Savestate::Resize(u32 new_length)
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{
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if (!buffer_owned)
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{ // If we're not allowed to resize this buffer...
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Log(LogLevel::Error, "savestate: Buffer is externally-owned, cannot resize it\n");
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return false;
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}
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u32 old_length = buffer_length;
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void* resized = realloc(buffer, new_length);
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if (!resized)
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{ // If the buffer couldn't be expanded...
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Log(LogLevel::Error, "savestate: Failed to resize owned savestate buffer from %dB to %dB\n", old_length, new_length);
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return false;
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}
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u32 length_diff = new_length - old_length;
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buffer = static_cast<u8 *>(resized);
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buffer_length = new_length;
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Log(LogLevel::Debug, "savestate: Expanded %uB savestate buffer to %uB\n", old_length, new_length);
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// Zero out the newly-allocated memory (to ensure we don't introduce a security hole)
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memset(buffer + old_length, 0, length_diff);
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return true;
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}
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void Savestate::WriteSavestateHeader()
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{
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// The magic number
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VarArray((void *) SAVESTATE_MAGIC, 4);
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// The major and minor versions
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u16 major = SAVESTATE_MAJOR;
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Var16(&major);
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u16 minor = SAVESTATE_MINOR;
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Var16(&minor);
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// The next 4 bytes are the file's length, which will be filled in at the end
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u32 zero = 0;
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Var32(&zero);
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// The following 4 bytes are reserved
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Var32(&zero);
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}
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void Savestate::WriteStateLength()
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{
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// Not to be confused with the buffer length.
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// The buffer might not be full,
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// so we don't want to write out the extra stuff.
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u32 state_length = buffer_offset;
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// Write the length in the header
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memcpy(buffer + 0x08, &state_length, sizeof(state_length));
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}
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u32 Savestate::FindSection(const char* magic) const
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{
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if (!magic) return NO_SECTION;
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// Start looking at the savestate's beginning, right after its global header
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// (we can't start from the current offset because then we'd lose the ability to rearrange sections)
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for (u32 offset = 0x10; offset < buffer_length;)
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{ // Until we've found the desired section...
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// Get this section's magic number
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char read_magic[4] = {0};
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memcpy(read_magic, buffer + offset, sizeof(read_magic));
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if (memcmp(read_magic, magic, sizeof(read_magic)) == 0)
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{ // If this is the right section...
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return offset + 16; // ...return the offset of the first byte of the section after the header
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}
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// Haven't found our section yet. Let's move on to the next one.
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u32 section_length_offset = offset + sizeof(read_magic);
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if (section_length_offset >= buffer_length)
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{ // If trying to read the section length would take us past the file's end...
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break;
|
||||
}
|
||||
|
||||
// First we need to find out how big this section is...
|
||||
u32 section_length = 0;
|
||||
memcpy(§ion_length, buffer + section_length_offset, sizeof(section_length));
|
||||
|
||||
// ...then skip it. (The section length includes the 16-byte header.)
|
||||
offset += section_length;
|
||||
}
|
||||
|
||||
// We've reached the end of the file without finding the requested section...
|
||||
Log(LogLevel::Error, "savestate: section %s not found. blarg\n", magic);
|
||||
return NO_SECTION;
|
||||
}
|
||||
Reference in New Issue
Block a user