Telit Delta Radio Firmware Upgrade support - libmts-io implementation

Changes after code review:

1. Handle cases when the number of bytes written is different from the number of bytes requested to transfer.
2. Use fstat instead of lseek to determine the firmware size.
3. Renamed TelitRadio::startWrite and TelitRadio::abortWrite functions to better represent their applicability scope.

3 files changed, 27 insertions, 16 deletions

diff --git a/include/mts/MTS_IO_TelitRadio.h b/include/mts/MTS_IO_TelitRadio.h
index c3ba764..ffdddd9 100644
--- a/include/mts/MTS_IO_TelitRadio.h
+++ b/include/mts/MTS_IO_TelitRadio.h
@@ -81,8 +81,8 @@ namespace MTS {
                 static const size_t FILE_CHUNK_SIZE;
                 static const std::string CMD_ABORT_UPLOAD;
 
-                CODE startWrite();
-                CODE abortWrite();
+                CODE startFotaWriteABD();
+                CODE abortFotaWriteABD();
 
                 static inline void callNextStep(UpdateCb& stepCb, const char* csMessage);
                 static inline void callNextStep(UpdateCb& stepCb, const std::string& sMessage);
diff --git a/src/MTS_IO_CellularRadio.cpp b/src/MTS_IO_CellularRadio.cpp
index 19f1b7b..49a2b32 100644
--- a/src/MTS_IO_CellularRadio.cpp
+++ b/src/MTS_IO_CellularRadio.cpp
@@ -21,6 +21,7 @@
 #include "mts/MTS_IO_CellularRadio.h"
 
 #include <unistd.h>
+#include <sys/stat.h>
 
 #include <mts/MTS_IO_MccMncTable.h>
 #include <mts/MTS_Thread.h>
@@ -1138,10 +1139,21 @@ ICellularRadio::CODE CellularRadio::sendData(const char* pData, size_t nBytes) {
         return ERROR;
     }
 
+    // This limit comes from the Connection::write implementation. Otherwise we can get overflows.
+    const size_t maxInt32 = INT32_MAX;    // iSize parameter type in Connection::write
+    const size_t maxUInt32 = UINT32_MAX;  // return value type in Connection::write
+    const size_t nSizeLimit = std::min(maxInt32, maxUInt32);
+
+    if (nBytes > nSizeLimit) {
+        printError("RADIO| Chunks larger than %d bytes are not supported", nSizeLimit);
+        return INVALID_ARGS;
+    }
+
+    // Now we can ignore conversion and overflow warnings emitted by compiler.
     int32_t iResult;
     iResult = m_apIo->write(pData, nBytes);
 
-    if(iResult == -1) {
+    if(iResult != static_cast<int32_t>(nBytes)) {
         printError("RADIO| Failed to send data to radio");
         return ERROR;
     }
@@ -1272,21 +1284,20 @@ ICellularRadio::CODE CellularRadio::getFileSize(int fd, size_t& nBytes) {
     CODE rc = FAILURE;
 
     do {
-        ssize_t dScrollPos;
-        dScrollPos = lseek(fd, 0, SEEK_SET);
-        if (dScrollPos < 0) {
-            printError("Failed to seek to the start of the file: %d", errno);
+        struct stat fileStatus;
+
+        // On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
+        if (fstat(fd, &fileStatus) < 0) {
+            printError("Failed to determine file size: %d", errno);
             break;
         }
 
-        dScrollPos = lseek(fd, 0, SEEK_END);
-        if (dScrollPos < 0) {
-            printError("Failed to determine the file size: %d", errno);
+        if (fileStatus.st_size < 0) {
+            printError("Failed to determine file size, file size is negative: %d", fileStatus.st_size);
             break;
         }
 
-        nBytes = static_cast<size_t>(dScrollPos);
-
+        nBytes = static_cast<size_t>(fileStatus.st_size);
         rc = SUCCESS;
 
     } while (false);
diff --git a/src/MTS_IO_TelitRadio.cpp b/src/MTS_IO_TelitRadio.cpp
index a82004c..8c7e174 100644
--- a/src/MTS_IO_TelitRadio.cpp
+++ b/src/MTS_IO_TelitRadio.cpp
@@ -943,7 +943,7 @@ ICellularRadio::CODE TelitRadio::fumoWriteGroupsABD(int fd, ICellularRadio::Upda
     printTrace("File size: %d bytes and %d chunks", dPayloadLength, nChunks);
     printTrace("Starting file upload...");
 
-    rc = startWrite();
+    rc = startFotaWriteABD();
     if (rc != SUCCESS) {
         return rc;
     }
@@ -980,12 +980,12 @@ ICellularRadio::CODE TelitRadio::fumoWriteGroupsABD(int fd, ICellularRadio::Upda
     }
 
     // send +++
-    abortWrite();
+    abortFotaWriteABD();
     return rc;
 }
 
 
-ICellularRadio::CODE TelitRadio::startWrite() {
+ICellularRadio::CODE TelitRadio::startFotaWriteABD() {
     const std::vector<std::string> vBailStrings{ ICellularRadio::RSP_CONNECT, ICellularRadio::RSP_ERROR };
     const int dTimeout = 1000; //ms
     std::string sCommand, sResult;
@@ -1001,7 +1001,7 @@ ICellularRadio::CODE TelitRadio::startWrite() {
     return SUCCESS;
 }
 
-ICellularRadio::CODE TelitRadio::abortWrite() {
+ICellularRadio::CODE TelitRadio::abortFotaWriteABD() {
     /*
      * To prevent the “+++” from being mistaken for data, the following sequence should be followed:
      * 1) Do not input any character within 1s or longer before inputting “+++”.