C语言写在磁盘中进行文件内数据的排序

下面是使用多路归并排序算法在磁盘中进行文件内数据的排序的C语言代码示例：

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

#define MAX_FILE_NUM 10   // 最多分成10个小文件
#define MAX_RECORD_NUM 10000  // 每个小文件最多10000个记录

// 定义记录结构体
typedef struct Record {
    int key;
    char value[256];
} Record;

// 定义归并排序函数
void mergeSort(Record* arr, int left, int right) {
    if (left >= right) {
        return;
    }
    int mid = (left + right) / 2;
    mergeSort(arr, left, mid);
    mergeSort(arr, mid + 1, right);
    Record* tmp = (Record*)malloc((right - left + 1) * sizeof(Record));
    int i = left, j = mid + 1, k = 0;
    while (i <= mid && j <= right) {
        if (arr[i].key <= arr[j].key) {
            tmp[k++] = arr[i++];
        } else {
            tmp[k++] = arr[j++];
        }
    }
    while (i <= mid) {
        tmp[k++] = arr[i++];
    }
    while (j <= right) {
        tmp[k++] = arr[j++];
    }
    for (i = left, k = 0; i <= right; i++, k++) {
        arr[i] = tmp[k];
    }
    free(tmp);
}

// 定义归并函数
void mergeFiles(char* file_prefix, int file_num, char* output_file) {
    char** file_names = (char**)malloc(file_num * sizeof(char*));
    int i;
    for (i = 0; i < file_num; i++) {
        file_names[i] = (char*)malloc(100 * sizeof(char));
        sprintf(file_names[i], "%s%d", file_prefix, i);
    }
    FILE** files = (FILE**)malloc(file_num * sizeof(FILE*));
    for (i = 0; i < file_num; i++) {
        files[i] = fopen(file_names[i], "r");
    }
    FILE* out_file = fopen(output_file, "w");
    Record** records = (Record**)malloc(file_num * sizeof(Record*));
    for (i = 0; i < file_num; i++) {
        records[i] = (Record*)malloc(MAX_RECORD_NUM * sizeof(Record));
        fread(records[i], sizeof(Record), MAX_RECORD_NUM, files[i]);
    }
    int* index = (int*)malloc(file_num * sizeof(int));
    for (i = 0; i < file_num; i++) {
        index[i] = 0;
    }
    int count = 0;
    while (count < file_num * MAX_RECORD_NUM) {
        int min_index = -1;
        Record min_record;
        for (i = 0; i < file_num; i++) {
            if (index[i] < MAX_RECORD_NUM) {
                if (min_index == -1 || records[i][index[i]].key < min_record.key) {
                    min_index = i;
                    min_record = records[i][index[i]];
                }
            }
        }
        fwrite(&min_record, sizeof(Record), 1, out_file);
        index[min_index]++;
        count++;
    }
    for (i = 0; i < file_num; i++) {
        fclose(files[i]);
        remove(file_names[i]);
    }
    fclose(out_file);
    for (i = 0; i < file_num; i++) {
        free(records[i]);
        free(file_names[i]);
    }
    free(records);
    free(files);
    free(file_names);
    free(index);
}

// 定义排序函数
void sortFile(char* input_file, char* output_file) {
    FILE* in_file = fopen(input_file, "r");
    int block_size = MAX_RECORD_NUM * sizeof(Record);
    char* buffer = (char*)malloc(block_size);
    int file_count = 0;
    while (!feof(in_file)) {
        int read_count = fread(buffer, sizeof(char), block_size, in_file);
        if (read_count > 0) {
            int record_count = read_count / sizeof(Record);
            Record* records = (Record*)buffer;
            mergeSort(records, 0, record_count - 1);
            char file_name[100];
            sprintf(file_name, "tmp%d", file_count++);
            FILE* out_file = fopen(file_name, "w");
            fwrite(records, sizeof(Record), record_count, out_file);
            fclose(out_file);
        }
    }
    fclose(in_file);
    mergeFiles("tmp", file_count, output_file);
    free(buffer);
}

// 测试代码
int main() {
    sortFile("input.txt", "output.txt");
    return 0;
}

上述代码中，我们首先定义了记录结构体，包括关键字和值。然后定义了归并排序函数和归并函数，用于对小文件进行排序和归并。最后定义了排序函数，该函数将输入文件分成多个小文件，并对每个小文件进行排序，然后将所有小文件进行归并得到有序的输出文件。

在测试代码中，我们调用了排序函数对输入文件进行排序，并将结果输出到输出文件中。其中输入文件为 "input.txt"，输出文件为 "output.txt"。