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util.ringbuffer: Add :sub() and :byte() methods equivalent to the string methods

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This commit is contained in:
Matthew Wild 2020-06-04 15:19:20 +01:00
parent a6c4ce73ef
commit 14a436817d
2 changed files with 160 additions and 1 deletions
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103
util-src/ringbuffer.c
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@ -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");
}