[英]Convert from UTF-8 to ISO8859-15 in C++
我想在C / C ++中完成从UTF-8到ISO 8859-15的转换,而无需包括其他库。
我该如何实现?
我发现以下代码适用于ISO 8859-1,但是我不确定如何处理ISO 8859-15和ISO 8859-1之间的差异( https://en.wikipedia.org/wiki/ ISO / IEC_8859-15 ):
std::string UTF8toISO8859_1(const char * in) {
std::string out;
if (in == NULL)
return out;
unsigned int codepoint;
while (*in != 0) {
unsigned char ch = static_cast<unsigned char>(*in);
if (ch <= 0x7f)
codepoint = ch;
else if (ch <= 0xbf)
codepoint = (codepoint << 6) | (ch & 0x3f);
else if (ch <= 0xdf)
codepoint = ch & 0x1f;
else if (ch <= 0xef)
codepoint = ch & 0x0f;
else
codepoint = ch & 0x07;
++in;
if (((*in & 0xc0) != 0x80) && (codepoint <= 0x10ffff)) {
if (codepoint <= 255) {
out.append(1, static_cast<char>(codepoint));
}
else {
out.append("?");
}
}
}
return out;
}
我喜欢这个代码。 太短了。 大多数代码只处理将多字节序列解码为代码点。 编码点解码后,转换为ISO-8859-1非常简单:
out.append(1, static_cast<char>(codepoint));
out.append("?");
因此,要使其适用于ISO-8859-15,需要更多代码来处理引入ISO-8859-15时已被替换的字符(请参阅比较ISO-8859-1和ISO-8859-15 )。 不幸的是,它大大增加了代码大小。
下面的代码应该很容易理解。 如果这是主要问题,可以对其进行优化以获得更好的性能。
std::string UTF8toISO8859_1(const char * in) {
std::string out;
if (in == NULL)
return out;
unsigned int codepoint;
while (*in != 0) {
unsigned char ch = static_cast<unsigned char>(*in);
if (ch <= 0x7f)
codepoint = ch;
else if (ch <= 0xbf)
codepoint = (codepoint << 6) | (ch & 0x3f);
else if (ch <= 0xdf)
codepoint = ch & 0x1f;
else if (ch <= 0xef)
codepoint = ch & 0x0f;
else
codepoint = ch & 0x07;
++in;
if (((*in & 0xc0) != 0x80) && (codepoint <= 0x10ffff)) {
// a valid codepoint has been decoded; convert it to ISO-8859-15
char outc;
if (codepoint <= 255) {
// codepoints up to 255 can be directly converted wit a few exceptions
if (codepoint != 0xa4 && codepoint != 0xa6 && codepoint != 0xa8
&& codepoint != 0xb4 && codepoint != 0xb8 && codepoint != 0xbc
&& codepoint != 0xbd && codepoint != 0xbe) {
outc = static_cast<char>(codepoint);
}
else {
outc = '?';
}
}
else {
// With a few exceptions, codepoints above 255 cannot be converted
if (codepoint == 0x20AC) {
outc = 0xa4;
}
else if (codepoint == 0x0160) {
outc = 0xa6;
}
else if (codepoint == 0x0161) {
outc = 0xa8;
}
else if (codepoint == 0x017d) {
outc = 0xb4;
}
else if (codepoint == 0x017e) {
outc = 0xb8;
}
else if (codepoint == 0x0152) {
outc = 0xbc;
}
else if (codepoint == 0x0153) {
outc = 0xbd;
}
else if (codepoint == 0x0178) {
outc = 0xbe;
}
else {
outc = '?';
}
}
out.append(1, outc);
}
}
return out;
}
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