Fix buffer writer

- Re-adding APIs for cbor_encoder_get_extra_bytes_needed() and
  cbor_encoder_get_buffer_size() as part of cbor_buf_writer APIs
- Add bytes_needed field to the buf writer

Author: vrahane

include/tinycbor/cbor_buf_writer.h

@@ -33,12 +33,28 @@ struct cbor_buf_writer {
     struct cbor_encoder_writer enc;
     uint8_t *ptr;
     const uint8_t *end;
+    int bytes_needed;
 };
 
 void cbor_buf_writer_init(struct cbor_buf_writer *cb, uint8_t *buffer,
                           size_t data);
 size_t cbor_buf_writer_buffer_size(struct cbor_buf_writer *cb,
                                    const uint8_t *buffer);
+
+CBOR_INLINE_API size_t cbor_encoder_get_extra_bytes_needed(const CborEncoder *encoder)
+{
+    struct cbor_buf_writer *wr = (struct cbor_buf_writer *)encoder->writer;
+
+    return wr->end ? 0 : (size_t)wr->bytes_needed;
+}
+
+CBOR_INLINE_API size_t cbor_encoder_get_buffer_size(const CborEncoder *encoder, const uint8_t *buffer)
+{
+    struct cbor_buf_writer *wr = (struct cbor_buf_writer *)encoder->writer;
+
+    return (size_t)(wr->ptr - buffer);
+}
+
 #ifdef __cplusplus
 }
 #endif

src/cbor_buf_writer.c

@@ -29,6 +29,9 @@ static inline int
 would_overflow(struct cbor_buf_writer *cb, size_t len)
 {
     ptrdiff_t remaining = (ptrdiff_t)cb->end;
+
+    if (!remaining)
+        return 1;
     remaining -= (ptrdiff_t)cb->ptr;
     remaining -= (ptrdiff_t)len;
     return (remaining < 0);
@@ -40,6 +43,14 @@ cbor_buf_writer(struct cbor_encoder_writer *arg, const char *data, int len)
     struct cbor_buf_writer *cb = (struct cbor_buf_writer *) arg;
 
     if (would_overflow(cb, len)) {
+        if (cb->end != NULL) {
+            len -= cb->end - cb->ptr;
+            cb->end = NULL;
+            cb->bytes_needed = 0;
+        }
+
+        cb->bytes_needed += len;
+
         return CborErrorOutOfMemory;
     }
 
@@ -55,6 +66,7 @@ cbor_buf_writer_init(struct cbor_buf_writer *cb, uint8_t *buffer, size_t size)
     cb->ptr = buffer;
     cb->end = buffer + size;
     cb->enc.bytes_written = 0;
+    cb->bytes_needed = 0;
     cb->enc.write = cbor_buf_writer;
 }
 

src/cborencoder.c

@@ -382,7 +382,7 @@ CborError cbor_encode_tag(CborEncoder *encoder, CborTag tag)
 static CborError encode_string(CborEncoder *encoder, size_t length, uint8_t shiftedMajorType, const void *string)
 {
     CborError err = encode_number(encoder, length, shiftedMajorType);
-    if (err && isOomError(err))
+    if (err && !isOomError(err))
         return err;
     return append_to_buffer(encoder, string, length);
 }

tests/encoder/tst_encoder.cpp

@@ -266,9 +266,9 @@ void compare(const QVariant &input, const QByteArray &output)
 
     QCOMPARE(int(encodeVariant(&encoder, input)), int(CborNoError));
     QCOMPARE(encoder.added, size_t(1));
-    //QCOMPARE(cbor_encoder_get_extra_bytes_needed(&encoder), size_t(0));
+    QCOMPARE(cbor_encoder_get_extra_bytes_needed(&encoder), size_t(0));
 
-    //buffer.resize(int(cbor_encoder_get_buffer_size(&encoder, bufptr)));
+    buffer.resize(int(cbor_encoder_get_buffer_size(&encoder, bufptr)));
     QCOMPARE(buffer, output);
 }
 
@@ -611,8 +611,8 @@ void tst_Encoder::shortBuffer()
         cbor_encoder_init(&encoder, &wr.enc, 0);
 
         QCOMPARE(int(encodeVariant(&encoder, input)), int(CborErrorOutOfMemory));
-        //QVERIFY(cbor_encoder_get_extra_bytes_needed(&encoder) != 0);
-        //QCOMPARE(len + cbor_encoder_get_extra_bytes_needed(&encoder), size_t(output.length()));
+        QVERIFY(cbor_encoder_get_extra_bytes_needed(&encoder) != 0);
+        QCOMPARE(len + cbor_encoder_get_extra_bytes_needed(&encoder), size_t(output.length()));
     }
 }
 

tests/tojson/tst_tojson.cpp

@@ -229,7 +229,7 @@ void compareOne_real(const QByteArray &data, const QString &expected, int flags,
     QCOMPARE(decoded, expected);
 
     // check that we consumed everything
-    //QCOMPARE((void*)first.ptr, (void*)data.constEnd());
+    QCOMPARE(cbor_value_at_end(&first), true);
 
     compareFailed = false;
 }
@@ -675,7 +675,7 @@ void compareMetaData(QByteArray data, const QString &expected, int otherFlags =
                  "\"; decoded stream:\n" + decoded.toLatin1());
 
         // check that we consumed everything
-        //QCOMPARE((void*)first.ptr, (void*)data.constEnd());
+        QCOMPARE(cbor_value_at_end(&first), true);
     }
 
     QVERIFY(decoded.startsWith("{\"v\":"));