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-rw-r--r--spec/util_ringbuffer_spec.lua58
-rw-r--r--util-src/ringbuffer.c103
2 files changed, 160 insertions, 1 deletions
diff --git a/spec/util_ringbuffer_spec.lua b/spec/util_ringbuffer_spec.lua
index 9512bfd4..72656899 100644
--- a/spec/util_ringbuffer_spec.lua
+++ b/spec/util_ringbuffer_spec.lua
@@ -24,4 +24,62 @@ describe("util.ringbuffer", function ()
assert.truthy(b:write("hi"));
end);
end);
+ describe(":sub", function ()
+ -- Helper function to compare buffer:sub() with string:sub()
+ local function test_sub(b, x, y)
+ local s = b:read(#b, true);
+ local string_result, buffer_result = s:sub(x, y), b:sub(x, y);
+ assert.equals(string_result, buffer_result, ("buffer:sub(%d, %s) does not match string:sub()"):format(x, y and ("%d"):format(y) or "nil"));
+ end
+
+ it("works", function ()
+ local b = rb.new();
+ b:write("hello world");
+ assert.equals("hello", b:sub(1, 5));
+ end);
+
+ it("supports optional end parameter", function ()
+ local b = rb.new();
+ b:write("hello world");
+ assert.equals("hello world", b:sub(1));
+ assert.equals("world", b:sub(-5));
+ end);
+
+ it("is equivalent to string:sub", function ()
+ local b = rb.new(6);
+ b:write("foobar");
+ b:read(3);
+ b:write("foo");
+ for i = -13, 13 do
+ for j = -13, 13 do
+ test_sub(b, i, j);
+ end
+ end
+ end);
+ end);
+
+ describe(":byte", function ()
+ -- Helper function to compare buffer:byte() with string:byte()
+ local function test_byte(b, x, y)
+ local s = b:read(#b, true);
+ local string_result, buffer_result = {s:byte(x, y)}, {b:byte(x, y)};
+ assert.same(string_result, buffer_result, ("buffer:byte(%d, %s) does not match string:byte()"):format(x, y and ("%d"):format(y) or "nil"));
+ end
+
+ it("is equivalent to string:byte", function ()
+ local b = rb.new(6);
+ b:write("foobar");
+ b:read(3);
+ b:write("foo");
+ test_byte(b, 1);
+ test_byte(b, 3);
+ test_byte(b, -1);
+ test_byte(b, -3);
+ for i = -13, 13 do
+ for j = -13, 13 do
+ test_byte(b, i, j);
+ end
+ end
+ end);
+ end);
end);
diff --git a/util-src/ringbuffer.c b/util-src/ringbuffer.c
index e15b66a6..07e1096f 100644
--- a/util-src/ringbuffer.c
+++ b/util-src/ringbuffer.c
@@ -2,7 +2,6 @@
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
-#include <stdio.h>
#include <lua.h>
#include <lauxlib.h>
@@ -15,6 +14,55 @@ typedef struct {
char buffer[];
} ringbuffer;
+/* Translate absolute idx to a wrapped index within the buffer,
+ based on current read position */
+static int wrap_pos(const ringbuffer *b, const long idx, long *pos) {
+ if(idx > (long)b->blen) {
+ return 0;
+ }
+ if(idx + (long)b->rpos > (long)b->alen) {
+ *pos = idx - (b->alen - b->rpos);
+ } else {
+ *pos = b->rpos + idx;
+ }
+ return 1;
+}
+
+static int calc_splice_positions(const ringbuffer *b, long start, long end, long *out_start, long *out_end) {
+ if(start < 0) {
+ start = 1 + start + b->blen;
+ }
+ if(start <= 0) {
+ start = 1;
+ }
+
+ if(end < 0) {
+ end = 1 + end + b->blen;
+ }
+
+ if(end > (long)b->blen) {
+ end = b->blen;
+ }
+ if(start < 1) {
+ start = 1;
+ }
+
+ if(start > end) {
+ return 0;
+ }
+
+ start = start - 1;
+
+ if(!wrap_pos(b, start, out_start)) {
+ return 0;
+ }
+ if(!wrap_pos(b, end, out_end)) {
+ return 0;
+ }
+
+ return 1;
+}
+
static void writechar(ringbuffer *b, char c) {
b->blen++;
b->buffer[(b->wpos++) % b->alen] = c;
@@ -178,6 +226,55 @@ static int rb_tostring(lua_State *L) {
return 1;
}
+static int rb_sub(lua_State *L) {
+ ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
+
+ long start = luaL_checkinteger(L, 2);
+ long end = luaL_optinteger(L, 3, -1);
+
+ long wrapped_start, wrapped_end;
+ if(!calc_splice_positions(b, start, end, &wrapped_start, &wrapped_end)) {
+ lua_pushstring(L, "");
+ } else if(wrapped_end <= wrapped_start) {
+ lua_pushlstring(L, &b->buffer[wrapped_start], b->alen - wrapped_start);
+ lua_pushlstring(L, b->buffer, wrapped_end);
+ lua_concat(L, 2);
+ } else {
+ lua_pushlstring(L, &b->buffer[wrapped_start], (wrapped_end - wrapped_start));
+ }
+
+ return 1;
+}
+
+static int rb_byte(lua_State *L) {
+ ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
+
+ long start = luaL_optinteger(L, 2, 1);
+ long end = luaL_optinteger(L, 3, start);
+
+ long i;
+
+ long wrapped_start, wrapped_end;
+ if(calc_splice_positions(b, start, end, &wrapped_start, &wrapped_end)) {
+ if(wrapped_end <= wrapped_start) {
+ for(i = wrapped_start; i < (long)b->alen; i++) {
+ lua_pushinteger(L, b->buffer[i]);
+ }
+ for(i = 0; i < wrapped_end; i++) {
+ lua_pushinteger(L, b->buffer[i]);
+ }
+ return wrapped_end + (b->alen - wrapped_start);
+ } else {
+ for(i = wrapped_start; i < wrapped_end; i++) {
+ lua_pushinteger(L, b->buffer[i]);
+ }
+ return wrapped_end - wrapped_start;
+ }
+ }
+
+ return 0;
+}
+
static int rb_length(lua_State *L) {
ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
lua_pushinteger(L, b->blen);
@@ -239,6 +336,10 @@ int luaopen_util_ringbuffer(lua_State *L) {
lua_setfield(L, -2, "size");
lua_pushcfunction(L, rb_length);
lua_setfield(L, -2, "length");
+ lua_pushcfunction(L, rb_sub);
+ lua_setfield(L, -2, "sub");
+ lua_pushcfunction(L, rb_byte);
+ lua_setfield(L, -2, "byte");
lua_pushcfunction(L, rb_free);
lua_setfield(L, -2, "free");
}