Ubuntu下C++使用icu库检测字符编码

Ubuntu下C++使用icu库检测字符编码。需先安装libicu-dev库：

sudo apt install libicu-dev

　　

C++代码如下：

//g++ -o x x.cpp -licuuc -licui18n
#include <stdio.h>
#include <string.h>

#include <unicode/ucnv.h>
#include <unicode/utypes.h>
#include <unicode/ucsdet.h>

#define BUF_MAX     4096

/*
 * data，    传入参数， 需要探测的字符串
 * len，     传入参数， 探测字符串长度
 * detected  传出参数， 探测的最有可能的字符编码名称, 调用者需要释放该字段
**/
bool detectTextEncoding(const char *data, int32_t len, char **detected) {
    UCharsetDetector *csd;
    const UCharsetMatch **csm;
    int32_t match, matchCount = 0;

    UErrorCode status = U_ZERO_ERROR;

    csd = ucsdet_open(&status);
    if (status != U_ZERO_ERROR)
        return false;

    ucsdet_setText(csd, data, len, &status);
    if (status != U_ZERO_ERROR)
        return false;

    csm = ucsdet_detectAll(csd, &matchCount, &status);
    if (status != U_ZERO_ERROR)
        return false;

#if 0 //打印出探测的可能的编码
    for(match = 0; match < matchCount; match += 1)
    {
        const char *name = ucsdet_getName(csm[match], &status);
        const char *lang = ucsdet_getLanguage(csm[match], &status);
        int32_t confidence = ucsdet_getConfidence(csm[match], &status);

        if (lang == NULL || strlen(lang) == 0)
                lang = "**";

        printf("%s (%s) %d
", name, lang, confidence);
    }
#endif

    if (matchCount > 0) {
        *detected = strdup(ucsdet_getName(csm[0], &status)); //分配了内存， 需要释放
        if (status != U_ZERO_ERROR)
            return false;
    }

    printf("charset = %s
", *detected);

    ucsdet_close(csd);
    return true;
}


/*
 * toConverterName,      转换后的字符编码
 * fromConverterName,    转换前的字符编码
 * target,               存储转换后的字符串， 传出参数
 * targetCapacity,       存储容量，target的大小
 * source，              需要转换的字符串
 * sourceLength,         source的大小
**/
int convert(const char *toConverterName, const char *fromConverterName,
            char *target, int32_t targetCapacity, const char *source, int32_t sourceLength) {
    UErrorCode error = U_ZERO_ERROR;
    ucnv_convert(toConverterName, fromConverterName, target, targetCapacity, source, sourceLength, &error);

    return error;
}

int main(int argc, char **argv) {
    if (argc <= 1) {
        printf("Usage: %s [filename]...
", argv[0]);
        return -1;
    }

    FILE *file;
    char *filename = argv[1];

    file = fopen(filename, "rb");
    if (file == NULL) {
        printf("Cannot open file "%s"

", filename);
        return -1;
    }

    int len = 0;
    char *detected = NULL;

    char *buffer = new char[BUF_MAX];
    char *target = new char[BUF_MAX * 2];

    while (true) {
        memset(buffer, 0, BUF_MAX);
        memset(target, 0, BUF_MAX * 2);

        len = (int32_t) fread(buffer, sizeof(char), BUF_MAX, file);

        if (detected == NULL) {
            if (!detectTextEncoding(buffer, len, &detected)) //编码探测
                break;
        }

        //转换为utf8字符编码
        if (convert("UTF-8", detected, target, BUF_MAX * 2, (const char *) buffer, len) != U_ZERO_ERROR) {
            printf("ucnv_convert error");
            break;
        }

        printf("%s", target); //打印出转换的文件的字符串

        if (len < BUF_MAX)
            break;
    }

    delete[] buffer;
    delete[] target;
    delete[] detected;
    fclose(file);

    return 0;
}

　　测试一下，正常检测出了当前文件编码：