Tidy up ringbuf and make tests

include/ucore/ringbuf.h

@@ -0,0 +1,98 @@
+#ifndef UC_RINGBUG_H_
+#define UC_RINGBUG_H_
+#include <stdint.h>
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct UCRingBuf UCRingBuf;
+struct UCRingBuf {
+    char *base;
+    uint32_t sz;
+    uint32_t read_idx;
+    uint32_t write_idx;
+};
+
+/**
+ * Creates a new ringbuffer of at least @sz length.
+ * The length will be rounded up to the neares page size
+ *
+ * The ringbuffer is implementd by mapping the same physical memory
+ * twice into virtual memory adjacent to eachother, avoiding
+ * a splitting up read/writes when the ringbuffer wraps around.
+ *
+ * This means accessing rb.base[rb.len] up to rb.base[rb.len * 2 - 1]
+ * is accessing the same memory as rb.base[0] up to rb.base[rb.len -1]
+ *
+ * @param rb UCRingBuf to initialize
+ * @param sz minimum length of the ring buffer
+ * @returns 0 on success
+ */
+int uc_ringbuf_init(UCRingBuf *rb, uint32_t sz);
+
+/** Free resources used by the ring buffer.
+ *
+ * @return 0 on success
+ */
+int uc_ringbuf_destroy(UCRingBuf *rb);
+
+/**
+ * Write data to the ringbuffer. The number of bytes to write must fit
+ * in the free space of the ringbuffer
+ *
+ * @param rb UCRingBuf to write to.
+ * @param data data to write
+ * @param sz number of bytes to write from data
+ * @return 0 on success
+ */
+int uc_ringbuf_write(UCRingBuf *rb, const void *restrict data, uint32_t sz);
+
+/** Read data from the ringbuffer
+ *
+ * @param rb UCRingBuf to write to.
+ * @param data buffer to copy data into
+ * @param sz number of bytes to read, must not exceed available data
+ *            in the buffer
+ * @return 0 on success
+ */
+int uc_ringbuf_read(UCRingBuf *rb, void *restrict data, uint32_t sz);
+
+
+/** Inspect how much free space is available for writing to the ring buffer
+ *
+ * @param rb UCRingBuf to inspect
+ * @returns number of free bytes
+ */
+uint32_t uc_ringbuf_available(const UCRingBuf *rb);
+
+/**
+ * Length of available data in the ringbuffer
+ *
+ * @param rb UCRingBuf get length of
+ *
+ * @return length of data available to read
+ */
+static inline uint32_t uc_ringbuf_len(const UCRingBuf *rb)
+{
+    return rb->write_idx - rb->read_idx;
+}
+
+/**
+ *  Get a pointer to the first unread byte
+ *  Caller is responsible for reading no more than the available
+ *  data
+ *
+ * @param rb UCRingBuf to peek into
+ *
+ * @returns pointer to first unread byte
+*/
+static inline void *uc_ringbuf_peek(const UCRingBuf *rb)
+{
+    return &rb->base[rb->read_idx];
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/ringbuf.c

@@ -0,0 +1,93 @@
+#ifdef __linux
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <sys/mman.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+#include "ucore/ringbuf.h"
+
+
+int uc_ringbuf_init(UCRingBuf *rb, uint32_t sz)
+{
+
+    uint32_t pagesz = getpagesize();
+    // Round up to page size
+    sz = ((sz + pagesz - 1) / pagesz) * pagesz;
+    /* Reserve contiguous address space*/
+    void *base = mmap(NULL, sz * 2, PROT_NONE, MAP_POPULATE|MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+    if (base == NULL) {
+        return -errno;
+    }
+    /* MAP_PRIVATE doesn't work */
+    base = mmap(base, sz * 1, PROT_READ|PROT_WRITE, MAP_POPULATE|MAP_ANONYMOUS|MAP_FIXED|MAP_SHARED, -1, 0);
+    if (base == MAP_FAILED) {
+        return -errno;
+    }
+    void *mbase = mremap(base, sz * 1, sz, MREMAP_FIXED|MREMAP_MAYMOVE|MREMAP_DONTUNMAP, base + sz);
+    if (mbase == MAP_FAILED) {
+        munmap(base, sz);
+        return -errno;
+
+    }
+
+    rb->base = base;
+    rb->sz = sz;
+    rb->read_idx = 0;
+    rb->write_idx = 0;
+
+    return 0;
+}
+
+int uc_ringbuf_destroy(UCRingBuf *rb)
+{
+    int rc = munmap(rb->base, rb->sz);
+    if (rc != 0) {
+        return -errno;
+    }
+
+    rc = munmap(rb->base + rb->sz, rb->sz);
+    if (rc != 0) {
+        return -errno;
+    }
+
+    rb->base = NULL;
+
+    return 0;
+}
+
+uint32_t uc_ringbuf_available(const UCRingBuf *rb)
+{
+    return rb->sz - rb->write_idx + rb->read_idx;
+}
+
+int uc_ringbuf_write(UCRingBuf *rb, const void *restrict data, uint32_t len)
+{
+    if (rb->write_idx - rb->read_idx + len > rb->sz) {
+        return -ENOMEM;
+    }
+    memcpy(&rb->base[rb->write_idx], data, len);
+    rb->write_idx += len;
+
+    return 0;
+}
+
+int uc_ringbuf_read(UCRingBuf *rb, void *restrict data, uint32_t len)
+{
+    if (uc_ringbuf_len(rb) < len) {
+        return -ENOMEM;
+    }
+
+    memcpy(data, &rb->base[rb->read_idx], len);
+
+    rb->read_idx += len;
+    if (rb->read_idx == rb->write_idx) {
+        rb->read_idx = rb->write_idx = 0;
+    } else if (rb->read_idx > rb->sz) {
+        rb->read_idx -= rb->sz;
+        rb->write_idx -= rb->sz;
+    }
+    return 0;
+}
+
+#endif

test/test_ringbuf.c

@@ -0,0 +1,48 @@
+#include <check.h>
+#include <unistd.h>
+#include "ucore/ringbuf.h"
+
+START_TEST (test_ringbuf)
+{
+
+    UCRingBuf rb;
+    int rc;
+    int pgsize = getpagesize();
+    rc = uc_ringbuf_init(&rb, pgsize);
+    ck_assert_int_eq(rc, 0);
+    ck_assert_int_eq(uc_ringbuf_available(&rb), pgsize);
+
+
+    for (int i = 0 ; i < pgsize; i++) {
+        unsigned char data = i % 256;
+        rc = uc_ringbuf_write(&rb, &data, 1);
+        ck_assert_int_eq(rc, 0);
+
+    }
+    ck_assert_int_eq(uc_ringbuf_available(&rb), 0);
+
+
+    for (int i = 0; i < pgsize; i++) {
+        unsigned char data = 0;
+        rc = uc_ringbuf_read(&rb, &data, 1);
+        ck_assert_int_eq(rc, 0);
+        ck_assert_int_eq(data, i % 256);
+    }
+    ck_assert_int_eq(uc_ringbuf_available(&rb), pgsize);
+
+}
+
+Suite *ringbuf_suite(void)
+{
+    Suite *s = suite_create("ringbuf");
+    TCase *tc1 = tcase_create("ringbuf");
+
+    tcase_add_test(tc1, test_ringbuf);
+#ifndef __APPLE__
+#endif
+
+    suite_add_tcase(s, tc1);
+
+    return s;
+}
+

test/test_runner.c

@@ -34,6 +34,7 @@ extern Suite *ticket_lock_suite(void);
 extern Suite *restart_counter_suite(void);
 extern Suite *iomux_suite(void);
 extern Suite *iomux_signal_suite(void);
+extern Suite *ringbuf_suite(void);
 
 static suite_func suites[] = {
     bitvec_suite,
@@ -62,7 +63,8 @@ static suite_func suites[] = {
     ticket_lock_suite,
     restart_counter_suite,
     iomux_suite,
-    iomux_signal_suite
+    iomux_signal_suite,
+    ringbuf_suite
 
 };