Split out txbuf and add unit test.

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "hw/mcu/microchip/samd/asf4"]
 	path = hw/mcu/microchip/samd/asf4
 	url = https://github.com/adafruit/asf4.git
+[submodule "tests/vendor/unity"]
+	path = tests/vendor/unity
+	url = https://github.com/ThrowTheSwitch/Unity.git

.travis.yml

@@ -19,3 +19,4 @@ before_script:
 script:
   - make -j2 -C examples/device/cdc_msc_hid BOARD=metro_m0_express
   - make -j2 -C examples/device/cdc_msc_hid BOARD=metro_m4_express
+  - cd tests/common && ceedling test:all

src/class/midi/midi_device.c

@@ -46,6 +46,7 @@
 //--------------------------------------------------------------------+
 #include "midi_device.h"
 #include "class/audio/audio.h"
+#include "common/tusb_txbuf.h"
 #include "device/usbd_pvt.h"
 
 //--------------------------------------------------------------------+
@@ -68,11 +69,8 @@ typedef struct
 
   // This is a ring buffer that aligns to word boundaries so that it can be transferred directly to
   // the USB peripheral. There are three states to the data: free, transmitting and pending.
-  CFG_TUSB_MEM_ALIGN uint8_t tx_buf[CFG_TUD_MIDI_TX_BUFSIZE];
-  uint16_t tx_buf_len;
-  uint16_t first_free;
-  uint16_t pending_count;
-  uint16_t transmitting_count;
+  CFG_TUSB_MEM_ALIGN uint8_t raw_tx_buffer[CFG_TUD_MIDI_TX_BUFSIZE];
+  tu_txbuf_t txbuf;
 
   // We need to pack messages into words before queueing their transmission so buffer across write
   // calls.
@@ -149,65 +147,6 @@ void midi_rx_done_cb(midid_interface_t* midi, uint8_t const* buffer, uint32_t bu
 // WRITE API
 //--------------------------------------------------------------------+
 
-uint16_t maybe_transmit(midid_interface_t* midi) {
-    if (midi->transmitting_count > 0 || midi->pending_count == 0) {
-        return 0;
-    }
-    midi->transmitting_count = midi->pending_count;
-    uint16_t transmit_start_index;
-    // The pending zone wraps back to the end so we must do two transfers.
-    if (midi->pending_count > midi->first_free) {
-        midi->transmitting_count -= midi->first_free;
-        transmit_start_index = midi->tx_buf_len - midi->transmitting_count;
-    } else {
-        transmit_start_index = midi->first_free - midi->transmitting_count;
-
-        // We are transmitting up to first free so ensure it's word aligned for the next transmit.
-        uint8_t over_aligned = midi->first_free % sizeof(size_t);
-        if (over_aligned != 0) {
-            midi->first_free = (midi->first_free + (sizeof(size_t) - midi->first_free)) % midi->tx_buf_len;
-        }
-    }
-    midi->pending_count -= midi->transmitting_count;
-
-    uint8_t* tx_start = midi->tx_buf + transmit_start_index;
-    if (!dcd_edpt_xfer(0, midi->ep_in, tx_start, midi->transmitting_count)) {
-        return 0;
-    }
-    return midi->transmitting_count;
-}
-
-uint32_t tud_tx_buf_write_done_cb(midid_interface_t* midi, uint32_t bufsize) {
-    midi->transmitting_count -= bufsize;
-
-    uint16_t len = maybe_transmit(midi);
-    return len;
-}
-
-uint32_t tud_tx_buf_write(midid_interface_t* midi, uint8_t const* buffer, uint32_t bufsize) {
-    uint32_t len;
-    int32_t last_free = midi->first_free - midi->pending_count - midi->transmitting_count;
-    if (last_free < 0) {
-        len = (last_free + midi->tx_buf_len) - midi->first_free;
-    } else {
-        len = midi->tx_buf_len - midi->first_free;
-    }
-    if (bufsize < len) {
-        len = bufsize;
-    }
-    memcpy(midi->tx_buf + midi->first_free, buffer, len);
-    // uint32_t remaining_bytes
-    // if (last_free > 0 && len < bufsize) {
-    //     if ()
-    //
-    // }
-    midi->first_free = (midi->first_free + len) % midi->tx_buf_len;
-    midi->pending_count += len;
-
-    maybe_transmit(midi);
-    return len;
-}
-
 uint32_t tud_midi_n_write(uint8_t itf, uint8_t jack_id, uint8_t const* buffer, uint32_t bufsize)
 {
   midid_interface_t* midi = &_midid_itf[itf];
@@ -265,7 +204,7 @@ uint32_t tud_midi_n_write(uint8_t itf, uint8_t jack_id, uint8_t const* buffer, u
     }
 
     if (midi->message_buffer_length == midi->message_target_length) {
-        tud_tx_buf_write(midi, midi->message_buffer, 4);
+        tu_txbuf_write_n(&midi->txbuf, midi->message_buffer, 4);
         midi->message_buffer_length = 0;
     }
     i++;
@@ -291,10 +230,7 @@ void midid_init(void)
     tu_fifo_config_mutex(&midi->rx_ff, osal_mutex_create(&midi->rx_ff_mutex));
     #endif
 
-    midi->tx_buf_len = CFG_TUD_MIDI_TX_BUFSIZE;
-    midi->first_free = 0;
-    midi->pending_count = 0;
-    midi->transmitting_count = 0;
+    tu_txbuf_config(&midi->txbuf, midi->raw_tx_buffer, CFG_TUD_MIDI_TX_BUFSIZE, dcd_edpt_xfer);
   }
 }
 
@@ -307,10 +243,7 @@ void midid_reset(uint8_t rhport)
     midid_interface_t* midi = &_midid_itf[i];
     tu_memclr(midi, ITF_MEM_RESET_SIZE);
     tu_fifo_clear(&midi->rx_ff);
-    midi->tx_buf_len = CFG_TUD_MIDI_TX_BUFSIZE;
-    midi->first_free = 0;
-    midi->pending_count = 0;
-    midi->transmitting_count = 0;
+    tu_txbuf_clear(&midi->txbuf);
   }
 }
 
@@ -356,6 +289,7 @@ bool midid_open(uint8_t rhport, tusb_desc_interface_t const * p_interface_desc,
         uint8_t ep_addr = ((tusb_desc_endpoint_t const *) p_desc)->bEndpointAddress;
         if (tu_edpt_dir(ep_addr) == TUSB_DIR_IN) {
             p_midi->ep_in = ep_addr;
+            tu_txbuf_set_ep_addr(&p_midi->txbuf, ep_addr);
         } else {
             p_midi->ep_out = ep_addr;
         }
@@ -401,7 +335,7 @@ bool midid_xfer_cb(uint8_t rhport, uint8_t edpt_addr, xfer_result_t result, uint
     // prepare for next
     TU_ASSERT( dcd_edpt_xfer(rhport, p_midi->ep_out, p_midi->epout_buf, CFG_TUD_MIDI_EPSIZE), false );
   } else if ( edpt_addr == p_midi->ep_in ) {
-    tud_tx_buf_write_done_cb(p_midi, xferred_bytes);
+    tu_txbuf_transmit_done_cb(&p_midi->txbuf, xferred_bytes);
   }
 
   // nothing to do with in and notif endpoint

src/common/tusb_txbuf.c

@@ -0,0 +1,159 @@
+/**************************************************************************/
+/*!
+    @file     tusb_txbuf.c
+    @author   Scott Shawcroft
+
+    @section LICENSE
+
+    Software License Agreement (BSD License)
+
+    Copyright (c) 2018, Scott Shawcroft
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions are met:
+    1. Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+    3. Neither the name of the copyright holders nor the
+    names of its contributors may be used to endorse or promote products
+    derived from this software without specific prior written permission.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
+    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
+    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+    INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION HOWEVER CAUSED AND
+    ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+    INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS
+    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+ This file is part of the tinyusb stack.
+ */
+/**************************************************************************/
+#include <stdio.h>
+#include <string.h>
+
+#include "tusb_txbuf.h"
+
+bool tu_txbuf_config(tu_txbuf_t *txbuf, uint8_t* buffer, uint16_t buffer_length, edpt_xfer xfer)
+{
+  txbuf->buffer = (uint8_t*) buffer;
+  txbuf->buf_len = buffer_length;
+  txbuf->first_free = 0;
+  txbuf->pending_count = 0;
+  txbuf->transmitting_count = 0;
+  txbuf->xfer = xfer;
+  txbuf->padding = 0;
+
+  return true;
+}
+
+uint16_t maybe_transmit(tu_txbuf_t* buf) {
+    if (buf->transmitting_count > 0 || buf->pending_count == 0) {
+        return 0;
+    }
+    buf->transmitting_count = buf->pending_count;
+    uint16_t transmit_start_index;
+    uint8_t over_aligned = 0;
+    // The pending zone wraps back to the end so we must do two transfers.
+    if (buf->pending_count > buf->first_free) {
+        buf->transmitting_count -= buf->first_free;
+        transmit_start_index = buf->buf_len - buf->transmitting_count;
+    } else {
+        transmit_start_index = buf->first_free - buf->transmitting_count;
+
+        // We are transmitting up to first free so ensure it's word aligned for the next transmit.
+        over_aligned = buf->first_free % sizeof(uint32_t);
+        buf->padding = sizeof(uint32_t) - over_aligned;
+        if (over_aligned != 0) {
+            buf->first_free = (buf->first_free + buf->padding) % buf->buf_len;
+        }
+    }
+    buf->pending_count -= buf->transmitting_count;
+
+    uint8_t* tx_start = buf->buffer + transmit_start_index;
+    if (!buf->xfer(0, buf->ep_addr, tx_start, buf->transmitting_count)) {
+        return 0;
+    }
+    return buf->transmitting_count;
+}
+
+uint32_t tu_txbuf_transmit_done_cb(tu_txbuf_t* buf, uint32_t bufsize) {
+    buf->transmitting_count -= bufsize;
+
+    return maybe_transmit(buf);
+}
+
+/******************************************************************************/
+/*!
+    @brief This function will write n elements into the array index specified by
+    the write pointer and increment the write index. If the write index
+    exceeds the max buffer size, then it will roll over to zero.
+
+    @param[in]  f
+                Pointer to the FIFO buffer to manipulate
+    @param[in]  p_data
+                The pointer to data to add to the FIFO
+    @param[in]  count
+                Number of element
+    @return Number of written elements
+*/
+/******************************************************************************/
+uint16_t tu_txbuf_write_n(tu_txbuf_t* txbuf, uint8_t const* buffer, uint32_t bufsize) {
+    uint32_t len;
+    int32_t last_free = txbuf->first_free - txbuf->pending_count - txbuf->transmitting_count - txbuf->padding;
+    if (last_free < 0) {
+        last_free += txbuf->buf_len;
+        len = last_free - txbuf->first_free;
+    } else {
+        len = txbuf->buf_len - txbuf->first_free;
+    }
+    if (bufsize < len) {
+        len = bufsize;
+    }
+    memcpy(txbuf->buffer + txbuf->first_free, buffer, len);
+    txbuf->first_free = (txbuf->first_free + len) % txbuf->buf_len;
+    txbuf->pending_count += len;
+    // Try to transmit now while we wrap the rest.
+    maybe_transmit(txbuf);
+    uint32_t remaining_bytes = bufsize - len;
+    if (remaining_bytes > 0 && last_free != txbuf->first_free) {
+        uint32_t second_len = remaining_bytes;
+        if (second_len > (uint32_t) last_free + 1) {
+            second_len = last_free + 1;
+        }
+        memcpy(txbuf->buffer, buffer + len, second_len);
+        txbuf->first_free = (txbuf->first_free + second_len) % txbuf->buf_len;
+        txbuf->pending_count += second_len;
+        len += second_len;
+    }
+
+    return len;
+}
+
+void tu_txbuf_set_ep_addr(tu_txbuf_t* txbuf, uint8_t ep_addr) {
+    txbuf->ep_addr = ep_addr;
+}
+
+/******************************************************************************/
+/*!
+    @brief Clear the txbuf including any currently transmitting data.
+
+    @param[in]  t
+                Pointer to the txbuf to manipulate
+*/
+/******************************************************************************/
+bool tu_txbuf_clear(tu_txbuf_t *txbuf)
+{
+
+  txbuf->first_free = 0;
+  txbuf->pending_count = 0;
+  txbuf->transmitting_count = 0;
+
+  return true;
+}

src/common/tusb_txbuf.h

@@ -0,0 +1,83 @@
+/**************************************************************************/
+/*!
+    @file     tusb_txbuf.h
+    @author   Scott Shawcroft
+
+    @section LICENSE
+
+    Software License Agreement (BSD License)
+
+    Copyright (c) 2018, Scott Shawcroft
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions are met:
+    1. Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+    3. Neither the name of the copyright holders nor the
+    names of its contributors may be used to endorse or promote products
+    derived from this software without specific prior written permission.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
+    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
+    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+    INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION HOWEVER CAUSED AND
+    ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+    INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS
+    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+	  This file is part of the tinyusb stack.
+*/
+/**************************************************************************/
+
+/** \ingroup Group_Common
+ * \defgroup group_txbuf txbuf
+ *  @{ */
+
+#ifndef _TUSB_TXBUF_H_
+#define _TUSB_TXBUF_H_
+
+#include <stdint.h>
+#include <stdbool.h>
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+typedef bool (*edpt_xfer) (uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes);
+
+
+/** \struct tu_txbuf_t
+ * \brief Circular transmit buffer that manages USB transfer memory. It is not threadsafe and is
+ *        only meant for use in the main task.
+ */
+typedef struct
+{
+    uint8_t* buffer    ; ///< buffer pointer
+    uint16_t buf_len;
+    uint16_t first_free;
+    uint16_t pending_count;
+    uint16_t transmitting_count;
+    uint16_t padding;
+    uint8_t ep_addr;
+    edpt_xfer xfer;
+} tu_txbuf_t;
+
+bool tu_txbuf_clear(tu_txbuf_t *f);
+bool tu_txbuf_config(tu_txbuf_t *f, uint8_t* buffer, uint16_t depth, edpt_xfer xfer);
+
+uint16_t tu_txbuf_write_n (tu_txbuf_t* txbuf, uint8_t const * buffer, uint32_t length);
+void tu_txbuf_set_ep_addr(tu_txbuf_t* txbuf, uint8_t ep_addr);
+uint32_t tu_txbuf_transmit_done_cb(tu_txbuf_t* buf, uint32_t bufsize);
+
+#ifdef __cplusplus
+ }
+#endif
+
+#endif /* _TUSB_TXBUF_H_ */

tests/common/Makefile

@@ -0,0 +1,91 @@
+ifeq ($(OS),Windows_NT)
+  ifeq ($(shell uname -s),) # not in a bash-like shell
+	CLEANUP = del /F /Q
+	MKDIR = mkdir
+  else # in a bash-like shell, like msys
+	CLEANUP = rm -f
+	MKDIR = mkdir -p
+  endif
+	TARGET_EXTENSION=.exe
+else
+	CLEANUP = rm -f
+	MKDIR = mkdir -p
+	TARGET_EXTENSION=out
+endif
+
+.PHONY: clean
+.PHONY: test
+
+PATHU = ../vendor/unity/src/
+PATHS = ../../src/
+PATHT = test/
+PATHB = build/
+PATHD = build/depends/
+PATHO = build/objs/
+PATHR = build/results/
+
+BUILD_PATHS = $(PATHB) $(PATHD) $(PATHO) $(PATHR)
+
+SRCT = $(wildcard $(PATHT)*.c)
+
+$(info $(SRCT))
+
+COMPILE=gcc -c
+LINK=gcc
+DEPEND=gcc -MM -MG -MF
+CFLAGS=-I. -I$(PATHU) -I$(PATHS) -DTEST
+
+RESULTS = $(patsubst $(PATHT)test%.c,$(PATHR)test%.txt,$(SRCT) )
+
+PASSED = `grep -s PASS $(PATHR)*.txt`
+FAIL = `grep -s FAIL $(PATHR)*.txt`
+IGNORE = `grep -s IGNORE $(PATHR)*.txt`
+
+test: $(BUILD_PATHS) $(RESULTS)
+	@echo "-----------------------\nIGNORES:\n-----------------------"
+	@echo "$(IGNORE)"
+	@echo "-----------------------\nFAILURES:\n-----------------------"
+	@echo "$(FAIL)"
+	@echo "-----------------------\nPASSED:\n-----------------------"
+	@echo "$(PASSED)"
+	@echo "\nDONE"
+
+$(PATHR)%.txt: $(PATHB)%.$(TARGET_EXTENSION)
+	-./$< > $@ 2>&1
+
+$(PATHB)test_%.$(TARGET_EXTENSION): $(PATHO)test_%.o $(PATHO)tusb_%.o $(PATHU)unity.o #$(PATHD)test%.d
+	$(LINK) -o $@ $^
+
+$(PATHO)%.o:: $(PATHT)%.c
+	$(COMPILE) $(CFLAGS) $< -o $@
+
+$(PATHO)%.o:: $(PATHS)common/%.c
+	$(COMPILE) $(CFLAGS) $< -o $@
+
+$(PATHO)%.o:: $(PATHU)%.c $(PATHU)%.h
+	$(COMPILE) $(CFLAGS) $< -o $@
+
+$(PATHD)%.d:: $(PATHT)%.c
+	$(DEPEND) $@ $<
+
+$(PATHB):
+	$(MKDIR) $(PATHB)
+
+$(PATHD):
+	$(MKDIR) $(PATHD)
+
+$(PATHO):
+	$(MKDIR) $(PATHO)
+
+$(PATHR):
+	$(MKDIR) $(PATHR)
+
+clean:
+	$(CLEANUP) $(PATHO)*.o
+	$(CLEANUP) $(PATHB)*.$(TARGET_EXTENSION)
+	$(CLEANUP) $(PATHR)*.txt
+
+.PRECIOUS: $(PATHB)test%.$(TARGET_EXTENSION)
+.PRECIOUS: $(PATHD)%.d
+.PRECIOUS: $(PATHO)%.o
+.PRECIOUS: $(PATHR)%.txt

tests/common/build/results/test_txbuf.txt

@@ -0,0 +1,8 @@
+test/test_txbuf.c:140:test_normal:PASS
+test/test_txbuf.c:141:test_nearly_full:PASS
+test/test_txbuf.c:142:test_wrap_around:PASS
+test/test_txbuf.c:143:test_wrap_around_too_much:PASS
+
+-----------------------
+4 Tests 0 Failures 0 Ignored 
+OK

tests/common/test/test_txbuf.c

@@ -0,0 +1,145 @@
+/**************************************************************************/
+/*!
+    @file     test_fifo.c
+    @author   Scott Shawcroft
+
+    @section LICENSE
+
+    Software License Agreement (BSD License)
+
+    Copyright (c) 2019, Scott Shawcroft
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions are met:
+    1. Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+    3. Neither the name of the copyright holders nor the
+    names of its contributors may be used to endorse or promote products
+    derived from this software without specific prior written permission.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
+    EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+    WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
+    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+    INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION HOWEVER CAUSED AND
+    ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+    INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS
+    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+    This file is part of the tinyusb stack.
+*/
+/**************************************************************************/
+
+#include "unity.h"
+#include "common/tusb_txbuf.h"
+
+uint32_t xfer_count = 0;
+uint32_t freshly_transmitted = 0;
+
+bool mock_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t* buffer, uint16_t total_bytes) {
+    TEST_ASSERT_EQUAL_INT_MESSAGE(0, ((size_t) buffer) % 4, "Transferred buffer not word aligned.");
+    xfer_count++;
+    freshly_transmitted += total_bytes;
+    return true;
+}
+
+tu_txbuf_t txbuf;
+__attribute__((aligned(4))) uint8_t buffer[16];
+
+uint8_t data[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16};
+
+void setUp(void) {
+    tu_txbuf_config(&txbuf, buffer, 16, mock_xfer);
+    tu_txbuf_set_ep_addr(&txbuf, 1);
+}
+
+void tearDown(void) {
+    xfer_count = 0;
+    freshly_transmitted = 0;
+}
+
+void xfer_callback(void) {
+    uint32_t previously_transmitted = freshly_transmitted;
+    freshly_transmitted = 0;
+
+    tu_tx_buf_transmit_done_cb(&txbuf, previously_transmitted);
+}
+
+// Test that we transfer immediately at the start and that the pointer is rounded to a word.
+void test_normal(void) {
+    uint16_t written = tu_txbuf_write_n(&txbuf, data, 4);
+    TEST_ASSERT_EQUAL_INT(4, written);
+    TEST_ASSERT_EQUAL_INT(1, xfer_count);
+    xfer_callback();
+    TEST_ASSERT_EQUAL_INT(1, xfer_count);
+}
+
+// Test that we only accept the data we have room for.
+void test_nearly_full(void) {
+    uint16_t written = tu_txbuf_write_n(&txbuf, data, 11);
+    TEST_ASSERT_EQUAL_INT(11, written);
+    TEST_ASSERT_EQUAL_INT(1, xfer_count);
+
+    written = tu_txbuf_write_n(&txbuf, data, 11);
+    // We only have space for 4 more bytes because 11 + padding are being written.
+    TEST_ASSERT_EQUAL_INT(4, written);
+
+    // Callback triggers a second write of remaining data.
+    xfer_callback();
+    TEST_ASSERT_EQUAL_INT(2, xfer_count);
+    TEST_ASSERT_EQUAL_INT(4, freshly_transmitted);
+}
+
+// Test that we only accept the data even when we have to wrap around.
+void test_wrap_around(void) {
+    uint16_t written = tu_txbuf_write_n(&txbuf, data, 11);
+    TEST_ASSERT_EQUAL_INT(11, written);
+    TEST_ASSERT_EQUAL_INT(1, xfer_count);
+    xfer_callback();
+    TEST_ASSERT_EQUAL_INT(1, xfer_count);
+
+    written = tu_txbuf_write_n(&txbuf, data, 11);
+    // We can queue all 11 bytes but they are split.
+    TEST_ASSERT_EQUAL_INT(11, written);
+    // Four immediately and seven more after the callback.
+    TEST_ASSERT_EQUAL_INT(2, xfer_count);
+    TEST_ASSERT_EQUAL_INT(4, freshly_transmitted);
+    xfer_callback();
+    TEST_ASSERT_EQUAL_INT(7, freshly_transmitted);
+    TEST_ASSERT_EQUAL_INT(3, xfer_count);
+}
+
+// Test that we only accept the data even when we have to wrap around.
+void test_wrap_around_too_much(void) {
+    uint16_t written = tu_txbuf_write_n(&txbuf, data, 11);
+    TEST_ASSERT_EQUAL_INT(11, written);
+    TEST_ASSERT_EQUAL_INT(1, xfer_count);
+    xfer_callback();
+    TEST_ASSERT_EQUAL_INT(1, xfer_count);
+
+    written = tu_txbuf_write_n(&txbuf, data, 17);
+    // We can queue 16 of 17 bytes but they are split.
+    TEST_ASSERT_EQUAL_INT(16, written);
+    // Four immediately and 12 more after the callback.
+    TEST_ASSERT_EQUAL_INT(2, xfer_count);
+    TEST_ASSERT_EQUAL_INT(4, freshly_transmitted);
+    xfer_callback();
+    TEST_ASSERT_EQUAL_INT(12, freshly_transmitted);
+    TEST_ASSERT_EQUAL_INT(3, xfer_count);
+}
+
+int main(void)
+{
+UNITY_BEGIN();
+RUN_TEST(test_normal);
+RUN_TEST(test_nearly_full);
+RUN_TEST(test_wrap_around);
+RUN_TEST(test_wrap_around_too_much);
+return UNITY_END();
+}

tests/vendor/unity

@@ -0,0 +1 @@
+Subproject commit a2849843654524194b72567b198c25d1c1dfead0