API Sysex fixes

Fix memory leaks by using stack instead of malloc
Reduce memory usage by having less temporary bufffers
Remove warnings by adding includes
Decrease code size by 608 bytes (mostly due to not linking malloc)
More robust handling of buffer overflows

2 files changed, 46 insertions, 16 deletions

diff --git a/quantum/api/api_sysex.c b/quantum/api/api_sysex.c
index a4a554e764..868f854b92 100644
--- a/quantum/api/api_sysex.c
+++ b/quantum/api/api_sysex.c
@@ -1,4 +1,6 @@
 #include "api_sysex.h"
+#include "sysex_tools.h"
+#include "print.h"
 
 void send_bytes_sysex(uint8_t message_type, uint8_t data_type, uint8_t * bytes, uint16_t length) {
     // SEND_STRING("\nTX: ");
@@ -6,24 +8,50 @@ void send_bytes_sysex(uint8_t message_type, uint8_t data_type, uint8_t * bytes,
     //     send_byte(bytes[i]);
     //     SEND_STRING(" ");
     // }
-    uint8_t * precode = malloc(sizeof(uint8_t) * (length + 2));
-    precode[0] = message_type;
-    precode[1] = data_type;
-    memcpy(precode + 2, bytes, length);
-    uint8_t * encoded = malloc(sizeof(uint8_t) * (sysex_encoded_length(length + 2)));
-    uint16_t encoded_length = sysex_encode(encoded, precode, length + 2);
-    uint8_t * array = malloc(sizeof(uint8_t) * (encoded_length + 5));
-    array[0] = 0xF0;
-    array[1] = 0x00;
-    array[2] = 0x00;
-    array[3] = 0x00;
-    array[encoded_length + 4] = 0xF7;
-    memcpy(array + 4, encoded, encoded_length);
-    midi_send_array(&midi_device, encoded_length + 5, array);
+    if (length > API_SYSEX_MAX_SIZE) {
+        xprintf("Sysex msg too big %d %d %d", message_type, data_type, length);
+        return;
+    }
+
+
+    // The buffer size required is calculated as the following
+    // API_SYSEX_MAX_SIZE is the maximum length
+    // In addition to that we have a two byte message header consisting of the message_type and data_type
+    // This has to be encoded with an additional overhead of one byte for every starting 7 bytes
+    // We just add one extra byte in case it's not divisible by 7
+    // Then we have an unencoded header consisting of 4 bytes
+    // Plus a one byte terminator
+    const unsigned message_header = 2;
+    const unsigned unencoded_message = API_SYSEX_MAX_SIZE + message_header;
+    const unsigned encoding_overhead = unencoded_message / 7 + 1;
+    const unsigned encoded_size = unencoded_message + encoding_overhead;
+    const unsigned unencoded_header = 4;
+    const unsigned terminator = 1;
+    const unsigned buffer_size = encoded_size + unencoded_header + terminator;
+    uint8_t buffer[encoded_size + unencoded_header + terminator];
+    // The unencoded header
+    buffer[0] = 0xF0;
+    buffer[1] = 0x00;
+    buffer[2] = 0x00;
+    buffer[3] = 0x00;
+
+    // We copy the message to the end of the array, this way we can do an inplace encoding, using the same
+    // buffer for both input and output
+    const unsigned message_size = length + message_header;
+    uint8_t* unencoded_start = buffer + buffer_size - message_size;
+    uint8_t* ptr = unencoded_start;
+    *(ptr++) = message_type;
+    *(ptr++) = data_type;
+    memcpy(ptr, bytes, length);
+
+    unsigned encoded_length = sysex_encode(buffer + unencoded_header, unencoded_start, message_size);
+    unsigned final_size = unencoded_header + encoded_length + terminator;
+    buffer[final_size - 1] = 0xF7;
+    midi_send_array(&midi_device, final_size, buffer);
 
     // SEND_STRING("\nTD: ");
     // for (uint8_t i = 0; i < encoded_length + 5; i++) {
-    //     send_byte(array[i]);
+    //     send_byte(buffer[i]);
     //     SEND_STRING(" ");
     // }
-}
\ No newline at end of file
+}
diff --git a/quantum/config_common.h b/quantum/config_common.h
index 17c11faeb6..4bdb2065d9 100644
--- a/quantum/config_common.h
+++ b/quantum/config_common.h
@@ -80,4 +80,6 @@
 #   endif
 #endif
 
+#define API_SYSEX_MAX_SIZE 32
+
 #endif