2021SC@SDUSC
前面几篇详细讲解了VFS的内存分配和共享缓存机制。
本篇将详细介绍各种字符串相互转换的方法及基于这些方法的公共包装器。
先看一个将UTF-8字符串与Microsoft Unicode相互转换的方法，由sqlite3_malloc()提供保存返回字符串的空间。
/*将utf-8字符串转换为microsoft Unicode。*/
static LPWSTR winUtf8ToUnicode(const char *zText){
int nChar;
LPWSTR zWideText;
nChar = osMultiByteToWideChar(CP_UTF8, 0, zText, -1, NULL, 0);
if( nChar==0 ){
return 0;
}
zWideText = sqlite3MallocZero( nChar*sizeof(WCHAR) );
if( zWideText==0 ){
return 0;
}
nChar = osMultiByteToWideChar(CP_UTF8, 0, zText, -1, zWideText,
nChar);
if( nChar==0 ){
sqlite3_free(zWideText);
zWideText = 0;
}
return zWideText;
}
对应的公共包装器如下：
LPWSTR sqlite3_win32_utf8_to_unicode(const char *zText){
#ifdef SQLITE_ENABLE_API_ARMOR
if( !zText ){
(void)SQLITE_MISUSE_BKPT;
return 0;
}
#endif
#ifndef SQLITE_OMIT_AUTOINIT
if( sqlite3_initialize() ) return 0;
#endif
return winUtf8ToUnicode(zText);
}
/*相应的，也将microsoft unicode字符串转换为utf-8。*/
static char *winUnicodeToUtf8(LPCWSTR zWideText){
int nByte;
char *zText;
nByte = osWideCharToMultiByte(CP_UTF8, 0, zWideText, -1, 0, 0, 0, 0);
if( nByte == 0 ){
return 0;
}
zText = sqlite3MallocZero( nByte );
if( zText==0 ){
return 0;
}
nByte = osWideCharToMultiByte(CP_UTF8, 0, zWideText, -1, zText, nByte, 0, 0);
if( nByte == 0 ){
sqlite3_free(zText);
zText = 0;
}
return zText;
}
对应的公共包装器如下：
char *sqlite3_win32_unicode_to_utf8(LPCWSTR zWideText){
#ifdef SQLITE_ENABLE_API_ARMOR
if( !zWideText ){
(void)SQLITE_MISUSE_BKPT;
return 0;
}
#endif
#ifndef SQLITE_OMIT_AUTOINIT
if( sqlite3_initialize() ) return 0;
#endif
return winUnicodeToUtf8(zWideText);
}
使用ANSI或OEM代码页将ANSI字符串转换为MicrosoftUnicode。
static LPWSTR winMbcsToUnicode(const char *zText, int useAnsi){
int nByte;
LPWSTR zMbcsText;
int codepage = useAnsi ? CP_ACP : CP_OEMCP;
nByte = osMultiByteToWideChar(codepage, 0, zText, -1, NULL,
0)*sizeof(WCHAR);
if( nByte==0 ){
return 0;
}
zMbcsText = sqlite3MallocZero( nByte*sizeof(WCHAR) );
if( zMbcsText==0 ){
return 0;
}
nByte = osMultiByteToWideChar(codepage, 0, zText, -1, zMbcsText,
nByte);
if( nByte==0 ){
sqlite3_free(zMbcsText);
zMbcsText = 0;
}
return zMbcsText;
}
使用ANSI或OEM代码页将MicrosoftUnicode字符串转换为多字节字符串
static char *winUnicodeToMbcs(LPCWSTR zWideText, int useAnsi){
int nByte;
char *zText;
int codepage = useAnsi ? CP_ACP : CP_OEMCP;
nByte = osWideCharToMultiByte(codepage, 0, zWideText, -1, 0, 0, 0, 0);
if( nByte == 0 ){
return 0;
}
zText = sqlite3MallocZero( nByte );
if( zText==0 ){
return 0;
}
nByte = osWideCharToMultiByte(codepage, 0, zWideText, -1, zText,
nByte, 0, 0);
if( nByte == 0 ){
sqlite3_free(zText);
zText = 0;
}
return zText;
}
将多字节字符串转换为UTF-8.
static char *winMbcsToUtf8(const char *zText, int useAnsi){
char *zTextUtf8;
LPWSTR zTmpWide;
zTmpWide = winMbcsToUnicode(zText, useAnsi);
if( zTmpWide==0 ){
return 0;
}
zTextUtf8 = winUnicodeToUtf8(zTmpWide);
sqlite3_free(zTmpWide);
return zTextUtf8;
}
对应的公共包装器如下：
char *sqlite3_win32_mbcs_to_utf8(const char *zText){
#ifdef SQLITE_ENABLE_API_ARMOR
if( !zText ){
(void)SQLITE_MISUSE_BKPT;
return 0;
}
#endif
#ifndef SQLITE_OMIT_AUTOINIT
if( sqlite3_initialize() ) return 0;
#endif
return winMbcsToUtf8(zText, osAreFileApisANSI());
}
将UTF-8字符串转换为多字节字符串.
static char *winUtf8ToMbcs(const char *zText, int useAnsi){
char *zTextMbcs;
LPWSTR zTmpWide;
zTmpWide = winUtf8ToUnicode(zText);
if( zTmpWide==0 ){
return 0;
}
zTextMbcs = winUnicodeToMbcs(zTmpWide, useAnsi);
sqlite3_free(zTmpWide);
return zTextMbcs;
}
对应的公共包装器如下：
char *sqlite3_win32_utf8_to_mbcs(const char *zText){
#ifdef SQLITE_ENABLE_API_ARMOR
if( !zText ){
(void)SQLITE_MISUSE_BKPT;
return 0;
}
#endif
#ifndef SQLITE_OMIT_AUTOINIT
if( sqlite3_initialize() ) return 0;
#endif
return winUtf8ToMbcs(zText, osAreFileApisANSI());
}