chore(driver): improve memory management in at driver (#140)

* chore(driver): improve memory management in at driver

* chore(driver): AT driver only supports linux

* chore: use malloc to allocate memory

* chore(driver): use macros instead of static variable

* fix: If memory allocation fails return -1

driver/CMakeLists.txt

@@ -2,7 +2,7 @@ include(CMakeDependentOption)
 cmake_dependent_option(LPAC_DYNAMIC_DRIVERS "Build lpac/libeuicc driver backends as a dynamic library" OFF "LPAC_DYNAMIC_LIBEUICC" OFF)
 
 option(LPAC_WITH_APDU_PCSC "Build APDU PCSC Backend (requires PCSC libraries)" ON)
-option(LPAC_WITH_APDU_AT "Build APDU AT Backend" ON)
+option(LPAC_WITH_APDU_AT "Build APDU AT Backend" Linux)
 option(LPAC_WITH_APDU_GBINDER "Build APDU Gbinder backend for libhybris devices (requires gbinder headers)" OFF)
 option(LPAC_WITH_APDU_QMI "Build QMI backend for Qualcomm devices (requires libqmi)" OFF)
 option(LPAC_WITH_APDU_QMI_QRTR "Build QMI-over-QRTR backend for Qualcomm devices (requires libqrtr and libqmi headers)" OFF)

driver/apdu/at.c

@@ -9,19 +9,21 @@
 #include <euicc/interface.h>
 #include <euicc/hexutil.h>
 
+#define AT_BUFFER_SIZE 20480
 static FILE *fuart;
 static int logic_channel = 0;
+static char *buffer;
 
 static int at_expect(char **response, const char *expected)
 {
-    char buffer[1024];
+    memset(buffer, 0, AT_BUFFER_SIZE);
 
     if (response)
         *response = NULL;
 
     while (1)
     {
-        fgets(buffer, sizeof(buffer), fuart);
+        fgets(buffer, AT_BUFFER_SIZE, fuart);
         buffer[strcspn(buffer, "\r\n")] = 0;
         if (getenv("AT_DEBUG"))
             printf("AT_DEBUG: %s\r\n", buffer);
@@ -210,6 +212,13 @@ static int libapduinterface_init(struct euicc_apdu_interface *ifstruct)
     ifstruct->logic_channel_close = apdu_interface_logic_channel_close;
     ifstruct->transmit = apdu_interface_transmit;
 
+    buffer = malloc(AT_BUFFER_SIZE);
+    if (!buffer)
+    {
+        fprintf(stderr, "Failed to allocate memory\n");
+        return -1;
+    }
+
     return 0;
 }
 
@@ -220,6 +229,7 @@ static int libapduinterface_main(int argc, char **argv)
 
 static void libapduinterface_fini(struct euicc_apdu_interface *ifstruct)
 {
+    free(buffer);
 }
 
 const struct euicc_driver driver_apdu_at = {