Official Solution
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef enum {
LOAD_SUCCESS = 0,
LOAD_ERR_PRIMARY_FAILED = -1,
LOAD_ERR_FALLBACK_FAILED = -2,
LOAD_ERR_INVALID_INPUT = -3
} LoadStatus;
/* Primary load method (preferred source) */
LoadStatus load_primary(const char *path, char *buffer, size_t size)
{
FILE *fp;
if (!path || !buffer || size == 0) {
return LOAD_ERR_INVALID_INPUT;
}
fp = fopen(path, "r");
if (!fp) {
return LOAD_ERR_PRIMARY_FAILED;
}
if (!fgets(buffer, size, fp)) {
fclose(fp);
return LOAD_ERR_PRIMARY_FAILED;
}
fclose(fp);
return LOAD_SUCCESS;
}
/* Fallback load method (secondary source) */
LoadStatus load_fallback(char *buffer, size_t size)
{
if (!buffer || size == 0) {
return LOAD_ERR_INVALID_INPUT;
}
/* Example fallback: built-in default data */
strncpy(buffer, "DEFAULT_DATA", size - 1);
buffer[size - 1] = ' ';
return LOAD_SUCCESS;
}
/* High-level loader with multi-level error handling */
LoadStatus load_data(const char *primary_path, char *buffer, size_t size)
{
LoadStatus status;
/* 1. Try primary method */
status = load_primary(primary_path, buffer, size);
if (status == LOAD_SUCCESS) {
return LOAD_SUCCESS;
}
fprintf(stderr, "Primary load failed, attempting fallback...n");
/* 2. Try fallback method */
status = load_fallback(buffer, size);
if (status == LOAD_SUCCESS) {
return LOAD_SUCCESS;
}
/* 3. All methods failed */
return LOAD_ERR_FALLBACK_FAILED;
}
/* Example usage */
int main(void)
{
char data[64];
LoadStatus result;
result = load_data("config.txt", data, sizeof(data));
if (result == LOAD_SUCCESS) {
printf("Loaded data: %sn", data);
} else {
printf("Data load failed, error code: %dn", result);
}
return 0;
}
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