Cellular: Added read hex string support to AT handler

Author: Mirela Chirica

features/cellular/framework/AT/ATHandler.cpp

@@ -25,9 +25,11 @@
 #include "rtos/Thread.h"
 #endif
 #include "Kernel.h"
+#include "CellularUtil.h"
 
 using namespace mbed;
 using namespace events;
+using namespace mbed_cellular_util;
 
 //#define MBED_TRACE_MAX_LEVEL TRACE_LEVEL_DEBUG
 #include "CellularLog.h"
@@ -511,6 +513,67 @@ ssize_t ATHandler::read_string(char *buf, size_t size, bool read_even_stop_tag)
     return len;
 }
 
+ssize_t ATHandler::read_hex_string(char *buf, size_t size)
+{
+    tr_debug("%s", __func__);
+    at_debug("\n----------read_hex_string buff:----------\n");
+    for (size_t i = _recv_pos; i < _recv_len; i++) {
+        at_debug("%c", _recv_buff[i]);
+    }
+    at_debug("\n----------read_hex_string end----------\n");
+
+    if (_last_err || !_stop_tag || _stop_tag->found) {
+        return -1;
+    }
+
+    size_t match_pos = 0, str_len = 0;
+    size_t upper = 0, lower = 0;
+    size_t hex_size = size*2;
+
+    uint8_t *pbuf = (uint8_t*)buf;
+
+    consume_char('\"');
+
+    for (size_t hex_len = 0; hex_len < (hex_size + match_pos); hex_len++) {
+        char c = get_char();
+        if (c == -1) {
+            pbuf[str_len] = '\0';
+            set_error(NSAPI_ERROR_DEVICE_ERROR);
+            return -1;
+        } else if (c == _delimiter) {
+            pbuf[str_len] = '\0';
+            break;
+        } else if (c == '\"') {
+            match_pos = 0;
+            if (str_len > 0) {
+                str_len--;
+            }
+            continue;
+        } else if (_stop_tag->len && c == _stop_tag->tag[match_pos]) {
+            match_pos++;
+            if (match_pos == _stop_tag->len) {
+                _stop_tag->found = true;
+                // remove tag from string if it was matched
+                str_len -= (_stop_tag->len - 1);
+                pbuf[str_len] = '\0';
+                break;
+            }
+        } else if (match_pos) {
+            match_pos = 0;
+        }
+
+        if (hex_len % 2 == 0) {
+            upper = hex_str_to_int(&c, 1);
+        } else {
+            lower = hex_str_to_int(&c, 1);
+            pbuf[str_len] = ((upper<<4) & 0xF0) | (lower & 0x0F);
+            str_len++;
+        }
+    }
+
+    return str_len;
+}
+
 int32_t ATHandler::read_int()
 {
     tr_debug("%s", __func__);

features/cellular/framework/AT/ATHandler.h

@@ -303,6 +303,17 @@ class ATHandler
      */
     ssize_t read_string(char *str, size_t size, bool read_even_stop_tag = false);
 
+    /** Reads chars representing hex ascii values and converts them to the corresponding chars.
+     *  For example: "4156" to "AV".
+     *  Terminates with null. Skips the quotation marks.
+     *  Stops on delimiter or stop tag.
+     *
+     *  @param str output buffer for the read
+     *  @param size maximum number of chars to output
+     *  @return length of output string or -1 in case of read timeout before delimiter or stop tag is found
+     */
+    ssize_t read_hex_string(char *str, size_t size);
+
     /** Reads as string and converts result to integer. Supports only positive integers.
      *
      *  @return the positive integer or -1 in case of error.

features/cellular/framework/targets/QUECTEL/BC95/QUECTEL_BC95_CellularStack.cpp

@@ -178,7 +178,6 @@ nsapi_size_or_error_t QUECTEL_BC95_CellularStack::socket_recvfrom_impl(CellularS
     nsapi_size_or_error_t recv_len=0;
     int port;
     char ip_address[NSAPI_IP_SIZE];
-    char *hexstr = new char[BC95_MAX_PACKET_SIZE*2+1];
 
     _at.cmd_start("AT+NSORF=");
     _at.write_int(socket->id);
@@ -190,13 +189,12 @@ nsapi_size_or_error_t QUECTEL_BC95_CellularStack::socket_recvfrom_impl(CellularS
     _at.read_string(ip_address, sizeof(ip_address));
     port = _at.read_int();
     recv_len = _at.read_int();
-    int hexlen = _at.read_string(hexstr, BC95_MAX_PACKET_SIZE*2+1);
+    int hexlen = _at.read_hex_string((char*)buffer, size);
     // remaining length
     _at.skip_param();
     _at.resp_stop();
 
     if (!recv_len || (recv_len == -1) || (_at.get_last_error() != NSAPI_ERROR_OK)) {
-        delete hexstr;
         return NSAPI_ERROR_WOULD_BLOCK;
     }
 
@@ -205,10 +203,8 @@ nsapi_size_or_error_t QUECTEL_BC95_CellularStack::socket_recvfrom_impl(CellularS
         address->set_port(port);
     }
 
-    if (hexlen > 0) {
-        hex_str_to_char_str((const char*) hexstr, hexlen, (char*)buffer);
+    if (recv_len != hexlen) {
+        tr_error("Not received as much data as expected. Should receive: %d bytes, received: %d bytes", recv_len, hexlen);
     }
-
-    delete hexstr;
     return recv_len;
 }