refactor(codec): use ssize_t for fl_base64_decode/encode return type

Change return type from int to ssize_t for consistency with POSIX
read/write conventions. Callers use ssize_t n instead of int n.

Print format stays %d with (int) cast for embedded libc compatibility.

Author: FASTSHIFT

App/func_loader/fl_cmd_file.c

@@ -91,8 +91,8 @@ fl_error_t fl_cmd_fwrite(fl_context_t* ctx, const cmd_args_t* args) {
 
     /* Write to file */
     ssize_t written = fl_file_write(&ctx->file_ctx, ctx->buf, n);
-    if (written < 0 || (int)written != n) {
-        fl_response(false, "Write failed, expected %d bytes, actual %d bytes", n, (int)written);
+    if (written < 0 || written != n) {
+        fl_response(false, "Write failed, expected %d bytes, actual %d bytes", (int)n, (int)written);
         return FL_ERR_IO;
     }
 

App/func_loader/fl_cmd_mem.c

@@ -76,7 +76,7 @@ fl_error_t fl_cmd_upload(fl_context_t* ctx, const cmd_args_t* args) {
     uint8_t* buf = ctx->buf;
     bool verify = args->crc >= 0;
 
-    int n = fl_base64_decode(args->data, buf, FL_BUF_SIZE);
+    ssize_t n = fl_base64_decode(args->data, buf, FL_BUF_SIZE);
     if (n < 0) {
         fl_response(false, "Invalid base64 data");
         return FL_ERR_ENCODE;
@@ -187,7 +187,7 @@ fl_error_t fl_cmd_write(fl_context_t* ctx, const cmd_args_t* args) {
     uint8_t* buf = ctx->buf;
     bool verify = args->crc >= 0;
 
-    int n = fl_base64_decode(args->data, buf, FL_BUF_SIZE);
+    ssize_t n = fl_base64_decode(args->data, buf, FL_BUF_SIZE);
     if (n < 0) {
         fl_response(false, "Invalid base64 data");
         return FL_ERR_ENCODE;

App/func_loader/fl_codec.c

@@ -75,7 +75,7 @@ static const uint8_t s_b64_dec[128] = {
 static const char s_b64_enc[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 /* clang-format on */
 
-int fl_base64_decode(const char* b64, uint8_t* out, size_t max) {
+ssize_t fl_base64_decode(const char* b64, uint8_t* out, size_t max) {
     if (!b64 || !out) {
         return -1;
     }
@@ -129,10 +129,10 @@ int fl_base64_decode(const char* b64, uint8_t* out, size_t max) {
         i += 4;
     }
 
-    return (int)out_len;
+    return (ssize_t)out_len;
 }
 
-int fl_base64_encode(const uint8_t* data, size_t len, char* out, size_t max) {
+ssize_t fl_base64_encode(const uint8_t* data, size_t len, char* out, size_t max) {
     if (!data || !out || max == 0) {
         return -1;
     }
@@ -155,5 +155,5 @@ int fl_base64_encode(const uint8_t* data, size_t len, char* out, size_t max) {
     }
     out[j] = '\0';
 
-    return (int)j;
+    return (ssize_t)j;
 }

App/func_loader/fl_codec.h

@@ -36,6 +36,7 @@ extern "C" {
 #include <stdint.h>
 #include <stddef.h>
 #include <string.h>
+#include <sys/types.h>
 
 /**
  * @brief  CRC-16-CCITT incremental calculation
@@ -65,7 +66,7 @@ static inline uint16_t fl_crc16_base_str(uint16_t crc, const char* str) {
  * @param  max Output buffer size
  * @return Number of decoded bytes, or -1 on error
  */
-int fl_base64_decode(const char* b64, uint8_t* out, size_t max);
+ssize_t fl_base64_decode(const char* b64, uint8_t* out, size_t max);
 
 /**
  * @brief  Encode bytes to Base64 string
@@ -75,7 +76,7 @@ int fl_base64_decode(const char* b64, uint8_t* out, size_t max);
  * @param  max  Output buffer size
  * @return Number of Base64 characters written, or -1 on error
  */
-int fl_base64_encode(const uint8_t* data, size_t len, char* out, size_t max);
+ssize_t fl_base64_encode(const uint8_t* data, size_t len, char* out, size_t max);
 
 #ifdef __cplusplus
 }