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我有一个问题，当我在一个 41 kb 的文件上使用它时，它被压缩（尽管因为它使用运行长度编码，它似乎总是使文件大小加倍）并正确解压缩。但是，当我尝试在一个 16,173 kb 的文件上使用它并解压缩它时，它没有打开，文件大小为 16,171 kb ......所以它解压缩了它，但它没有恢复到原来的形式.. ..有些事情搞砸了....让我感到困惑，我似乎无法弄清楚我做错了什么....

使用的方法是游程编码，它将每个字节替换为后跟字节的计数。

前：

46 6F 6F 20 62 61 72 21 21 21 20 20 20 20 20

后：

01 46 02 6F 01 20 01 62 01 61 01 72 03 21 05 20

这是我的代码：

    void compress_file(FILE *fp_in, FILE *fp_out)
    {
        int count, ch, ch2;

        ch = getc(fp_in);
        for (count = 0; ch2 != EOF; count = 0) {
            // if next byte is the same increase count and test again
            do {
                count++;           // set binary count
                ch2 = getc(fp_in); // set next variable for comparison
            } while (ch2 != EOF && ch2 == ch);
            // write bytes into new file
            putc(count, fp_out);
            putc(ch, fp_out);
            ch = ch2;
        }
        fclose(fp_in);
        fclose(fp_out);
        fprintf(stderr, "File Compressed\n");
    }

    void uncompress_file(FILE *fp_in, FILE *fp_out)
    {
        int count, ch, ch2;

        for (count = 0; ch2 != EOF; count = 0) {
            ch = getc(fp_in);   // grab first byte
            ch2 = getc(fp_in);  // grab second byte
            // write the bytes
            do {
                putc(ch2, fp_out);
                count++;
            } while (count < ch);
        }
        fclose(fp_in);
        fclose(fp_out);
        fprintf(stderr, "File Decompressed\n");
    }
4

2 回答 2

6

你错过了检查你的运行长度计数是否有字符溢出，所以如果你的文件中有超过 255 个相同的字符，这将出错。

于 2014-06-18T10:03:00.740 回答
1

这是工作源代码：

    // Chapter 22 Programming Project #7

    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    #include <ctype.h>

    void compress_file(FILE *fp_in, FILE *fp_out);
    void uncompress_file(FILE *fp_in, FILE *fp_out);

    int main(void)
    {
        FILE *fp_in, *fp_out;
        char nm_in[FILENAME_MAX], nm_out[FILENAME_MAX];
        int chk;

        for (;;) {
            printf(" ----------------------------------------- \n");
            printf("|             1 - Compress                |\n");
            printf("|             2 - Decompress              |\n");
            printf("|             3 - Exit                    |\n");
            printf(" ----------------------------------------- \n");
            do {
                printf("Enter a command: ");
                scanf(" %d", &chk);
            } while (isalpha(chk));

            if (chk == 3)
                exit(EXIT_SUCCESS);

            printf("Enter input file name: ");
            scanf(" %s", nm_in);
            printf("Enter output file name: ");
            scanf(" %s", nm_out);
            // Open file to read from
            while ((fp_in = fopen(nm_in, "rb")) == NULL) {
                fprintf(stderr, "Can't open \"%s\"\n", nm_in);
                printf("Enter input file name: ");
                scanf(" %s", nm_in);
            }
            // Open file to write to
            while ((fp_out = fopen(nm_out, "wb")) == NULL) {
                fprintf(stderr, "Can't create \"%s\"\n", nm_out);
                printf("Enter output file name: ");
                scanf(" %s", nm_out);
            }
            switch(chk) {
                case 1: compress_file(fp_in, fp_out); break;
                case 2: uncompress_file(fp_in, fp_out); break;
            }
            putchar('\n');
        }

        return 0;
    }

    void compress_file(FILE *fp_in, FILE *fp_out)
    {
        int count, ch, ch2, chk;

        ch = getc(fp_in);
        ch2 = ch;
        while (ch2 != EOF) {
            // if next byte is the same increase count and test
            for (count = 0; ch2 == ch && count < 255; count++) {
                ch2 = getc(fp_in); // set next variable for comparison
            }
            // write bytes into new file
            putc(count, fp_out);
            putc(ch, fp_out);
            ch = ch2;
        }
        fclose(fp_in);
        fclose(fp_out);
        fprintf(stderr, "File Compressed\n");
    }

    void uncompress_file(FILE *fp_in, FILE *fp_out)
    {
        int count, ch, ch2;

        for (count = 0; ch2 != EOF; count = 0) {
            ch = getc(fp_in);   // grab first byte
            ch2 = getc(fp_in);  // grab second byte
            // write the bytes
            do {
                putc(ch2, fp_out);
                count++;
            } while (count < ch);
        }
        fclose(fp_in);
        fclose(fp_out);
        fprintf(stderr, "File Decompressed\n");
    }
于 2014-06-18T16:20:28.993 回答