如何將字符“G”轉換為字符串“47”（十六進制）

Question

我想從標准輸入讀取一個字符串，將其保存在一個數組中，進行轉換，使其與指定的測試相匹配：

expected = "45 76 65 72 79 20"

自星期五以來，我已經嘗試了所有我能找到的解決方案，除了我不明白如何使用的strtol 。

    char input;
    char *buffer = NULL;
    char chunk[2];
    size_t stringLength = 0;
    int n = 0;

    while(fgets(chunk, 2, stdin) != NULL){
        stringLength += strlen(chunk);
    }
    rewind(stdin);

    buffer = (char *) malloc(stringLength + 1);
    if (buffer == NULL)
        exit(EXIT_FAILURE);

    while(scanf("%c", &input) == 1) {
        snprintf(buffer+n, 2, "%c", input); 
        n += strlen(chunk);
    }

    //code to convert char array buffer to array of hex separated by spaces

從 stdin = "Every P";

字符串我需要 output 才能通過示例測試： = "45 76 65 72 79 20 50";

如果我犯了任何錯誤，請告訴我，我已經學習如何編寫 C 代碼 1 1/2 個月了。

提前致謝！

Answer 1

AFAIK， rewind(stdin)是有問題的。 另一種選擇是使用realloc一次增加一個字符的數組。

int c;
char *s = NULL;
int char_count = 0;

// Read one char at a time, ignoring new line
while (EOF != (c = getc(stdin))) {
    // Ignore CR (i.e. Windows)
    if ('\r' == c) continue;
    // Consume the newline but don't add to buffer
    if ('\n' == c) break;
    // Grow array by 1 char (acts like malloc if pointer is NULL)
    s = realloc(s, ++char_count);
    // TODO handle error if (s == NULL) 
    // Append to array
    s[char_count - 1] = (char)c;
}

// Create the buffer for the hex string
// 3 chars for each letter -> 2 chars for hex + 1 for space
// First one does not get a space but we can use the extra +1 for \0
char *hex = malloc(char_count * 3);
// TODO handle error if (hex == NULL)
// Create a temporary pointer that we can increment while "hex" remains unchanged
char *temp = hex;
for (int i = 0; i < char_count; i++) {
    // No space on first char
    if (i == 0) {
        sprintf(temp, "%02X", s[i]);
        temp += 2;
    }
    else {
        sprintf(temp, " %02X", s[i]);
        temp += 3;
    }
}
*temp = '\0';

printf("%s\n", hex);

// Cleanup
free(s);
free(hex);

輸入： Every P
Output： 45 76 65 72 79 20 50

---

如果您只想將stdin重新打印為十六進制，則根本不需要任何緩沖區：

int c;
int char_count = 0;

// Read one char at a time and print as hex
while (EOF != (c = getc(stdin))) {
    // No space on first char
    if (0 == char_count++) {
        printf("%02X", c);
    }
    else {
        printf(" %02X", c);
    }
}
puts("");  // If you need a newline at the end