From 3df15584d6663b330c344068dce7d36c6f27cf4b Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Thu, 25 Apr 2024 21:46:31 +0200
Subject: Kernel: Add a ringbuffer

This will be used later
---
 kernel/lib/ringbuffer.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/lib/ringbuffer.h | 16 +++++++++
 2 files changed, 110 insertions(+)
 create mode 100644 kernel/lib/ringbuffer.c
 create mode 100644 kernel/lib/ringbuffer.h

(limited to 'kernel/lib')

diff --git a/kernel/lib/ringbuffer.c b/kernel/lib/ringbuffer.c
new file mode 100644
index 0000000..425971d
--- /dev/null
+++ b/kernel/lib/ringbuffer.c
@@ -0,0 +1,94 @@
+#include <assert.h>
+#include <kmalloc.h>
+#include <lib/ringbuffer.h>
+#include <math.h>
+#include <string.h>
+
+int ringbuffer_init(struct ringbuffer *rb, u32 buffer_size) {
+  rb->buffer_size = 0;
+  rb->read_ptr = 0;
+  rb->write_ptr = 0;
+  rb->buffer = kmalloc(buffer_size);
+  if (!rb->buffer) {
+    return 0;
+  }
+  rb->buffer_size = buffer_size;
+  return 1;
+}
+
+u32 ringbuffer_write(struct ringbuffer *rb, const u8 *buffer, u32 len) {
+  const u32 orig_len = len;
+  for (; len > 0;) {
+    u32 buffer_left;
+    if (rb->write_ptr >= rb->read_ptr) {
+      buffer_left = rb->buffer_size - rb->write_ptr;
+      if (0 == rb->read_ptr && buffer_left > 0) {
+        buffer_left--;
+      }
+    } else {
+      buffer_left = (rb->read_ptr - rb->write_ptr - 1);
+    }
+
+    if (0 == buffer_left) {
+      break;
+    }
+
+    u32 write_len = min(len, buffer_left);
+    write_len = min(write_len, rb->buffer_size - rb->write_ptr);
+    memcpy(rb->buffer + rb->write_ptr, buffer, write_len);
+    buffer += write_len;
+    len -= write_len;
+    rb->write_ptr = (rb->write_ptr + write_len) % rb->buffer_size;
+  }
+  return orig_len - len;
+}
+
+u32 ringbuffer_read(struct ringbuffer *rb, u8 *buffer, u32 len) {
+  const u32 orig_len = len;
+  for (; len > 0;) {
+    if (rb->read_ptr == rb->write_ptr) {
+      break;
+    }
+    u32 read_len;
+    if (rb->read_ptr >= rb->write_ptr) {
+      read_len = rb->buffer_size - rb->read_ptr;
+    } else if (rb->read_ptr < rb->write_ptr) {
+      read_len = rb->write_ptr - rb->read_ptr;
+    }
+    read_len = min(len, read_len);
+
+    memcpy(buffer, rb->buffer + rb->read_ptr, read_len);
+    len -= read_len;
+    buffer += read_len;
+    rb->read_ptr = (rb->read_ptr + read_len) % rb->buffer_size;
+  }
+  return orig_len - len;
+}
+
+void ringbuffer_free(struct ringbuffer *rb) {
+  kfree(rb->buffer);
+  rb->buffer = NULL;
+  rb->buffer_size = 0;
+  rb->write_ptr = 0;
+  rb->read_ptr = 0;
+}
+
+#ifdef KERNEL_TEST
+void ringbuffer_test(void) {
+  char buffer[4096];
+  struct ringbuffer rb;
+  assert(ringbuffer_init(&rb, 6));
+  assert(2 == ringbuffer_write(&rb, "ab", 2));
+  assert(2 == ringbuffer_write(&rb, "cd", 2));
+  assert(1 == ringbuffer_write(&rb, "ef", 2));
+  assert(0 == ringbuffer_write(&rb, "gh", 2));
+  assert(2 == ringbuffer_read(&rb, buffer, 2));
+  assert(0 == memcmp(buffer, "ab", 2));
+  assert(2 == ringbuffer_read(&rb, buffer, 2));
+  assert(0 == memcmp(buffer, "cd", 2));
+  assert(1 == ringbuffer_read(&rb, buffer, 2));
+  assert(0 == memcmp(buffer, "e", 1));
+  assert(0 == ringbuffer_read(&rb, buffer, 2));
+  ringbuffer_free(&rb);
+}
+#endif // KERNEL_TEST
diff --git a/kernel/lib/ringbuffer.h b/kernel/lib/ringbuffer.h
new file mode 100644
index 0000000..c329af3
--- /dev/null
+++ b/kernel/lib/ringbuffer.h
@@ -0,0 +1,16 @@
+#include <typedefs.h>
+
+struct ringbuffer {
+  u8 *buffer;
+  u32 buffer_size;
+  u32 read_ptr;
+  u32 write_ptr;
+};
+
+int ringbuffer_init(struct ringbuffer *rb, u32 buffer_size);
+u32 ringbuffer_write(struct ringbuffer *rb, const u8 *buffer, u32 len);
+u32 ringbuffer_read(struct ringbuffer *rb, u8 *buffer, u32 len);
+void ringbuffer_free(struct ringbuffer *rb);
+#ifdef KERNEL_TEST
+void ringbuffer_test(void);
+#endif // KERNEL_TEST
-- 
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