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Fix bug with wrong hashing of rencache commands 

The command in rencache.c (Command struct + variable length text) was
incorrectly sized. As a result some bites at the end of the command payload
were uninitialized and was causing hash to randomly change forcing the
system to redraw many more areas.

Since the text of the command for DRAW_TEXT commands is written beginning
at the offset of the text field we compute the bare size of the command as
offsetof(Command, text) instead of sizeof(Command).
This commit is contained in:
Francesco Abbate 2021-04-20 21:54:05 +02:00
parent cb28b5fa31
commit c97fa9a3a6
1 changed files with 7 additions and 5 deletions
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12
src/rencache.c
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@ -1,3 +1,4 @@
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include "rencache.h"
@ -11,6 +12,7 @@
#define CELLS_Y 50
#define CELL_SIZE 96
#define COMMAND_BUF_SIZE (1024 * 512)
#define COMMAND_BARE_SIZE offsetof(Command, text)
enum { FREE_FONT, SET_CLIP, DRAW_TEXT, DRAW_RECT, DRAW_TEXT_SUBPIXEL };
@ -91,7 +93,7 @@ static Command* push_command(int type, int size) {
return NULL;
}
command_buf_idx = n;
memset(cmd, 0, sizeof(Command));
memset(cmd, 0, COMMAND_BARE_SIZE);
cmd->type = type;
cmd->size = size;
return cmd;
@ -114,20 +116,20 @@ void rencache_show_debug(bool enable) {
void rencache_free_font(RenFont *font) {
Command *cmd = push_command(FREE_FONT, sizeof(Command));
Command *cmd = push_command(FREE_FONT, COMMAND_BARE_SIZE);
if (cmd) { cmd->font = font; }
}
void rencache_set_clip_rect(RenRect rect) {
Command *cmd = push_command(SET_CLIP, sizeof(Command));
Command *cmd = push_command(SET_CLIP, COMMAND_BARE_SIZE);
if (cmd) { cmd->rect = intersect_rects(rect, screen_rect); }
}
void rencache_draw_rect(RenRect rect, RenColor color) {
if (!rects_overlap(screen_rect, rect)) { return; }
Command *cmd = push_command(DRAW_RECT, sizeof(Command));
Command *cmd = push_command(DRAW_RECT, COMMAND_BARE_SIZE);
if (cmd) {
cmd->rect = rect;
cmd->color = color;
@ -148,7 +150,7 @@ int rencache_draw_text(RenFont *font,
if (rects_overlap(screen_rect, rect)) {
int sz = strlen(text) + 1;
Command *cmd = push_command(draw_subpixel ? DRAW_TEXT_SUBPIXEL : DRAW_TEXT, sizeof(Command) + sz);
Command *cmd = push_command(draw_subpixel ? DRAW_TEXT_SUBPIXEL : DRAW_TEXT, COMMAND_BARE_SIZE + sz);
if (cmd) {
memcpy(cmd->text, text, sz);
cmd->color = color;