sjis-fullwidth-ascii.hh

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/*
 
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Copyright (c) 2026 PCSX-Redux authors
 
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#pragma once
 
#include <stdint.h>
 
// Lightweight default title encoder: the ASCII-only subset of the BIOS
// save-title convention. Printable ASCII is promoted to its fullwidth form and
// looked up in a compact 95-entry table (190 bytes) carved out of the full
// Unicode->Shift-JIS table; any non-ASCII codepoint becomes '?'. This is what
// lets a program that only ever uses ASCII titles avoid linking the ~28kB
// c_unicodeToSjisConvTable. Registering the full encoder (see
// sjis-title-encoder.h) overrides this with the complete conversion.
//
// The table below is generated: for each ASCII value 0x20..0x7e it holds the
// Shift-JIS encoding of the corresponding fullwidth codepoint (space -> U+3000,
// 0x21..0x7e -> U+ff01..U+ff5e), taken verbatim from c_unicodeToSjisConvTable.
// Five fullwidth punctuation forms (" ' - \ ~) have no JIS X 0208 mapping, so
// their entries are 0 and the encoder emits '?' for them -- identical to what
// the full encoder does, keeping ASCII output byte-for-byte the same either way.
 
namespace Sjis {
 
// Indexed by (ASCII codepoint - 0x20), so [0] is space and [94] is '~'.
extern const uint16_t c_fullwidthAsciiToSjis[96];
 
// Encodes a UTF-8 string to Shift-JIS using the BIOS save-title convention,
// but with ASCII-only support: printable ASCII is promoted to fullwidth via the
// table above; every non-ASCII codepoint (and the five unmapped fullwidth forms)
// becomes '?'. Writes up to dstSize bytes, returns the number written; output is
// not NUL-terminated. Signature matches Sjis::utf8ToSjisTitle so the two are
// interchangeable behind a function pointer.
uint32_t asciiToSjisTitle(uint8_t* dst, uint32_t dstSize, const char* src);
 
// Decodes a Shift-JIS save title back to plain ASCII, the inverse of
// asciiToSjisTitle: each fullwidth form in the compact table becomes its ASCII
// character, and anything else (real Japanese, halfwidth kana, an unmapped
// form) becomes '?'. It uses only the 190-byte fullwidth table, so an ASCII-only
// program can read titles back without linking the full ~28kB conversion table;
// Sjis::sjisToUtf8 (sjis-decode.h) is the full-Unicode counterpart. Writes at
// most dstSize bytes, always NUL-terminating when dstSize > 0, and returns the
// number written (not counting the terminator). A 0x00 byte ends the input
// (0x00 is never a Shift-JIS lead or trail byte), giving a C string for the
// padded 64-byte card title field.
uint32_t sjisTitleToAscii(char* dst, uint32_t dstSize, const uint8_t* src, uint32_t srcLen);
 
}  // namespace Sjis