C大杂烩

标识未用变量，消除编译警告

#define UNUSED(x) (void)(x)

获取文件内容到一个字符串

#include <stdlib.h>
#include <assert.h>

char *getFileContent(char *filename) {
    FILE *f = fopen(filename, "rt");
    assert(f);
    fseek(f, 0, SEEK_END);
    size_t length = (size_t) ftell(f);
    fseek(f, 0, SEEK_SET);
    char *buffer = (char *) malloc(length + 1);
    buffer[length] = '\0';
    fread(buffer, 1, length, f);
    fclose(f);
    return buffer;
}

C语言变参

C语言的可变参数函数必须有至少一个固定参数，因为va_start要以这个参数为基址寻找其他参数。而且函数并不知道传递进来的参数个数，需要自己判断处理

例如:

GLuint createProgram(int count, ...) {
    GLuint program = glCreateProgram();
    va_list args;
    va_start(args, count);
    for (int i = 0; i < count; ++i) {
        GLuint arg = va_arg(args, GLuint);
        glAttachShader(program, arg);
    }
    va_end(args);
    glLinkProgram(program);
    return program;
}

遍历文件夹

#include <stdio.h>
#include <dirent.h>

int main(int argc, char *argv[]) {
    struct dirent *cursor;
    DIR *dir = opendir(".");
    while ((cursor = readdir(dir)) != NULL) {
        printf("%s\n", cursor->d_name);
    }
    closedir(dir);
}

#include <gtk/gtk.h>

int main(int argc, char *argv[]) {
    GDir *dir = g_dir_open(".", 0, NULL);
    const gchar *filename;
    while ((filename = g_dir_read_name(dir))) {
        printf("%s\n", filename);
    }
}

正则表达式

#include <gtk/gtk.h>

int main(int argc, char *argv[]) {
    GDir *dir = g_dir_open("/Users/bj/Dropbox/sample/music", 0, NULL);
    const gchar *filename;
    GRegex *regex = g_regex_new("(.+)\\.(mp3|wma|ogg)", 0, 0, NULL);
    while ((filename = g_dir_read_name(dir))) {
        GMatchInfo *matchInfo;
        g_regex_match(regex, filename, 0, &matchInfo);
        if (g_match_info_matches(matchInfo)) {
            printf("Matches: %s\n", g_match_info_fetch(matchInfo, 1));
        }
    }
}