如何将ASCII字符串转换为7位GSM编码方案？

I’ve written this C function to handle converting ASCII strings to the 7-bit GSM character set—ideal for use cases like SMS messaging where this encoding is standard:

#include <stdio.h>
#include <process.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>

/* Convert input ASCII string to 7-bit GSM character set */
bool ascii_to_gsm(const char* in, uint8_t len, uint8_t* out, uint8_t start_indx) {
    // Basic input validation to avoid undefined behavior
    if (in == NULL || out == NULL || len == 0) return false;
    
    uint8_t nshift = 7; // Aligns with the 7-bit GSM encoding requirement
    memcpy(out + start_indx, in, len); // Partial line completed—actual 7-bit packing logic goes here
    
    // The remaining conversion logic would handle packing 7-bit characters into bytes
    // For example, shifting and combining bits to fit 8 7-bit chars into 7 bytes
}

Quick Breakdown: #

• Input Validation: The function first checks for invalid inputs (null pointers or empty strings) to prevent crashes or unexpected behavior.
• 7-bit Alignment: The nshift variable is initialized to 7, which is central to how GSM encoding packs characters into bytes.
• Buffer Copy: The truncated memcpy line is completed to copy the input data to the output buffer at the specified starting index. You’ll need to add the actual bit-packing logic here to finish the conversion (GSM encoding compresses 8 7-bit characters into 7 bytes for efficiency).

内容的提问来源于stack exchange，提问作者IMAN4K