From 97a4879bc88861b718a5a45b4515303a81923db0 Mon Sep 17 00:00:00 2001
From: rsiddharth <s@ricketyspace.net>
Date: Mon, 16 Sep 2019 19:33:33 -0400
Subject: nserver: Add ringbuffer.h

---
 nserver/src/ringbuffer.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++
 nserver/src/ringbuffer.h | 61 ++++++++++++++++++++++++++++++++++
 2 files changed, 146 insertions(+)
 create mode 100644 nserver/src/ringbuffer.c
 create mode 100644 nserver/src/ringbuffer.h

diff --git a/nserver/src/ringbuffer.c b/nserver/src/ringbuffer.c
new file mode 100644
index 0000000..a2dc97f
--- /dev/null
+++ b/nserver/src/ringbuffer.c
@@ -0,0 +1,85 @@
+#undef NDEBUG
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <dbg.h>
+#include <ringbuffer.h>
+
+RingBuffer *RingBuffer_create(int length)
+{
+    RingBuffer *buffer = calloc(1, sizeof(RingBuffer));
+    buffer->length = length + 1;
+    buffer->start = 0;
+    buffer->end = 0;
+    buffer->buffer = calloc(buffer->length, 1);
+
+    return buffer;
+}
+
+void RingBuffer_destroy(RingBuffer *buffer)
+{
+    if (buffer) {
+        free(buffer->buffer);
+        free(buffer);
+    }
+}
+
+int RingBuffer_write(RingBuffer *buffer, char *data, int length)
+{
+    if (RingBuffer_available_data(buffer) == 0) {
+        buffer->start = buffer->end = 0;
+    }
+
+    check(length <= RingBuffer_available_space(buffer),
+          "Not enough space: %d request, %d available",
+          RingBuffer_available_data(buffer), length);
+
+    void *result = memcpy(RingBuffer_ends_at(buffer), data, length);
+    check(result != NULL, "Failed to write data into buffer");
+
+    RingBuffer_commit_write(buffer, length);
+
+    return length;
+ error:
+    return -1;
+}
+
+int RingBuffer_read(RingBuffer *buffer, char *target, int amount)
+{
+    check_debug(amount <= RingBuffer_available_data(buffer),
+                "Not enough in the buffer: has %d, needs %d",
+                RingBuffer_available_data(buffer), amount);
+
+    void *result =  memcpy(target, RingBuffer_starts_at(buffer), amount);
+    check(result != NULL, "Failed to write buffer into data.");
+
+    RingBuffer_commit_read(buffer, amount);
+
+    if (buffer->end == buffer->start) {
+        buffer->start = buffer->end = 0;
+    }
+
+    return amount;
+ error:
+    return -1;
+}
+
+bstring RingBuffer_gets(RingBuffer *buffer, int amount)
+{
+    check(amount > 0, "Need more than 0 for gets, you gave: %d",
+          amount);
+    check_debug(amount <= RingBuffer_available_data(buffer),
+                "Not enough in the buffer");
+
+    bstring result = blk2bstr(RingBuffer_starts_at(buffer), amount);
+    check(result != NULL, "Failed to create gets result.");
+    check(blength(result) == amount, "Wrong result length.");
+
+    RingBuffer_commit_read(buffer, amount);
+    assert(RingBuffer_available_data(buffer) >= 0
+           && "Error in read commit");
+    return result;
+ error:
+    return NULL;
+}
diff --git a/nserver/src/ringbuffer.h b/nserver/src/ringbuffer.h
new file mode 100644
index 0000000..154abc3
--- /dev/null
+++ b/nserver/src/ringbuffer.h
@@ -0,0 +1,61 @@
+#ifndef _RingBuffer_h
+#define _RingBuffer_h
+
+#include <bstrlib.h>
+
+typedef struct {
+    char *buffer;
+    int length;
+    int start;
+    int end;
+} RingBuffer;
+
+RingBuffer *RingBuffer_create(int length);
+
+void RingBuffer_destroy(RingBuffer *buffer);
+
+int RingBuffer_read(RingBuffer *buffer, char *target, int amount);
+
+int RingBuffer_write(RingBuffer *buffer, char *data, int length);
+
+int RingBuffer_empty(RingBuffer *buffer);
+
+int RingBuffer_full(RingBuffer *buffer);
+
+int RingBuffer_available_data(RingBuffer *buffer);
+
+int RingBuffer_available_space(RingBuffer *buffer);
+
+bstring RingBuffer_gets(RingBuffer *buffer, int amount);
+
+#define RingBuffer_available_data(B) (\
+        ((B)->end + 1) % (B)->length - (B)->start - 1)
+
+#define RingBuffer_available_space(B) (\
+        (B)->length - (B)->end - 1)
+
+#define RingBuffer_full(B) (RingBuffer_available_data((B))\
+                            - (B)->length == 0)
+
+#define RingBuffer_empty(B) (\
+        RingBuffer_available_data((B)) == 0)
+
+#define RingBuffer_puts(B, D) RingBuffer_write(\
+        (B), bdata((D)), blength((D)))
+
+#define RingBuffer_get_all(B) RingBuffer_gets(\
+        (B), RingBuffer_available_data((B)))
+
+#define RingBuffer_starts_at(B) (\
+        (B)->buffer + (B)->start)
+
+#define RingBuffer_ends_at(B) (\
+        (B)->buffer + (B)->end)
+
+#define RingBuffer_commit_read(B,A) (\
+        (B)->start = ((B)->start  + (A)) % (B)->length)
+
+#define RingBuffer_commit_write(B, A) (\
+    (B)->end  = ((B)->end + (A)) % (B)->length)
+
+#endif
-- 
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