From 2bdcaf319b1d74ffbaccf08a58336f804761beab Mon Sep 17 00:00:00 2001
From: LLLL Colonq <llll@colonq>
Date: Thu, 9 Jul 2026 23:51:55 -0400
Subject: Refactor into monorepo

---
 qoi/src/qoi.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 qoi/src/qoi.c

(limited to 'qoi/src/qoi.c')

diff --git a/qoi/src/qoi.c b/qoi/src/qoi.c
new file mode 100644
index 0000000..52545c9
--- /dev/null
+++ b/qoi/src/qoi.c
@@ -0,0 +1,112 @@
+#include <lcq/qoi.h>
+
+/* encoder */
+static void write_u32_be(qoi_encoder *q) {
+}
+
+/* decoder */
+static u32 read_u32_be(qoi_decoder *q) {
+    u32 ret = 0;
+    if (q->cur + 4 >= q->len) return 0xffffffff;
+    ret |= q->buf[q->cur++] << 24;
+    ret |= q->buf[q->cur++] << 16;
+    ret |= q->buf[q->cur++] << 8;
+    ret |= q->buf[q->cur++];
+    return ret;
+}
+typedef enum {
+    QOI_OP_INVALID = -3,
+    QOI_OP_RGB = -2,
+    QOI_OP_RGBA = -1,
+    QOI_OP_INDEX = 0,
+    QOI_OP_DIFF = 1,
+    QOI_OP_LUMA = 2,
+    QOI_OP_RUN = 3
+} qoi_op;
+static qoi_op cur_op(qoi_decoder *q) {
+    u8 v;
+    if (q->cur >= q->len) return QOI_OP_INVALID;
+    v = q->buf[q->cur];
+    if ((i8) v == QOI_OP_RGB) return QOI_OP_RGB;
+    if ((i8) v == QOI_OP_RGBA) return QOI_OP_RGBA;
+    return v >> 6;
+}
+void qoi_decoder_new(qoi_decoder *q, u8 *buf, i64 len) {
+    i64 i;
+    q->buf = buf;
+    q->len = len;
+    q->cur = 0;
+    for (i = 0; i < 64; ++i) q->palette[i] = qoi_color_new(0, 0, 0, 0);
+}
+bool qoi_decode_header(qoi_decoder *q, qoi_header *h) {
+    if (q->cur + 14 > q->len) return false;
+    if (read_u32_be(q) != ('q' << 24 | 'o' << 16 | 'i' << 8 | 'f')) {
+        return false;
+    }
+    h->width = read_u32_be(q);
+    h->height = read_u32_be(q);
+    h->channels = q->buf[q->cur++];
+    h->colorspace = q->buf[q->cur++];
+    return true;
+}
+bool qoi_decode(qoi_decoder *q, qoi_header *h, qoi_color *pixels) {
+    i64 len = h->width * h->height;
+    i64 pidx = 0;
+    qoi_color c = qoi_color_new(0, 0, 0, 255);
+    u8 v = 0, w = 0;
+    u8 padding[8] = {0, 0, 0, 0, 0, 0, 0, 1};
+    i64 i;
+    for (i = 0; i < 8; ++i) if (padding[i] != q->buf[q->len - 8 + i]) return false;
+    while (q->cur < q->len - 8 && pidx < len) {
+        /* we never need to range-check q->cur mid-loop, since we know the padding exists */
+        switch (cur_op(q)) {
+        case QOI_OP_INVALID: return false;
+        case QOI_OP_RGB:
+            q->cur++;
+            c.r = q->buf[q->cur++];
+            c.g = q->buf[q->cur++];
+            c.b = q->buf[q->cur++];
+            pixels[pidx++] = c;
+            break;
+        case QOI_OP_RGBA:
+            q->cur++;
+            c.r = q->buf[q->cur++];
+            c.g = q->buf[q->cur++];
+            c.b = q->buf[q->cur++];
+            c.a = q->buf[q->cur++];
+            pixels[pidx++] = c;
+            break;
+        case QOI_OP_INDEX:
+            v = q->buf[q->cur++] & 0x3f /* 0b111111 */;
+            c = q->palette[v];
+            pixels[pidx++] = c;
+            break;
+        case QOI_OP_DIFF: {
+            v = q->buf[q->cur++];
+            c.r += (u8) ((v >> 4 & 0x3) - 2);
+            c.g += (u8) ((v >> 2 & 0x3) - 2);
+            c.b += (u8) ((v & 0x3) - 2);
+            pixels[pidx++] = c;
+            break;
+        }
+        case QOI_OP_LUMA: {
+            v = (q->buf[q->cur++] & 0x3f) - 32;
+            w = q->buf[q->cur++];
+            c.r += (u8) (((w >> 4) & 0xf) - 8 + v);
+            c.g += v;
+            c.b += (u8) ((w & 0xf) - 8 + v);
+            pixels[pidx++] = c;
+            break;
+        }
+        case QOI_OP_RUN:
+            v = (q->buf[q->cur++] & 0x3f) + 1;
+            for (; v > 0; v--) {
+                pixels[pidx++] = c;
+            }
+            break;
+        default: return false;
+        }
+        q->palette[qoi_color_hash(c)] = c;
+    }
+    return true;
+}
-- 
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