From 3af50b956b8887b64c3c29b30a0008be866b24c4 Mon Sep 17 00:00:00 2001
From: the lemons <citrons@mondecitronne.com>
Date: Sun, 5 Feb 2023 19:06:16 -0600
Subject: initial commit

---
 memview.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 memview.c

(limited to 'memview.c')

diff --git a/memview.c b/memview.c
new file mode 100644
index 0000000..c2af3ac
--- /dev/null
+++ b/memview.c
@@ -0,0 +1,124 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <assert.h>
+#include <limits.h>
+#include <string.h>
+#include <SDL.h>
+
+#include "memview.h"
+#include "procfs.h"
+
+struct viewer {
+	int fd;
+	SDL_Renderer *renderer;
+	SDL_Texture *page_texture;
+	uint8_t page_buffer[PAGE_SIZE];
+};
+
+enum color {
+	BLACK = 0x00000000,
+	WHITE = 0xFFFFFFFF,
+	GREY = 0xFF303030,
+};
+
+#define BIT_OF(X, I) (((X) >> (I)) & 1ULL)
+
+static uintptr_t zorder(int x, int y) {
+	uintptr_t z = 0;
+	unsigned int ux, uy;
+	memcpy(&ux, &x, sizeof(unsigned int));
+	memcpy(&uy, &y, sizeof(unsigned int));
+	// interleaving bits results in a point on the z-order curve
+	for (int i = 0; i < sizeof(x) * CHAR_BIT; i++)
+		z |= (BIT_OF(ux, i) << i*2) | (BIT_OF(uy, i) << (i*2 + 1));
+	return z;
+}
+
+static void unzorder(uintptr_t z, int *x, int *y) {
+	unsigned int ux, uy = 0;
+	for (int i = 0; i < sizeof(z) * CHAR_BIT / 2; i++) {
+		ux |= BIT_OF(z, i*2) << i;
+		uy |= BIT_OF(z, i*2 + 1) << i;
+	}
+	memcpy(x, &ux, sizeof(int));
+	memcpy(y, &uy, sizeof(int));
+}
+
+uintptr_t to_addr(int x, int y) {
+	uintptr_t page = zorder(x / PAGE_WIDTH, y / PAGE_HEIGHT);
+	int offset = x % PAGE_WIDTH + y % PAGE_HEIGHT * PAGE_WIDTH;
+	return page * PAGE_SIZE + offset;
+}
+
+void to_pos(uintptr_t addr,  int *x, int *y) {
+	int px, py;
+	unzorder(addr / PAGE_SIZE, &px, &py);
+	int offset = addr % PAGE_SIZE;
+	*x = px * PAGE_WIDTH + offset % PAGE_WIDTH;
+	*y = py * PAGE_HEIGHT + offset / PAGE_WIDTH;
+}
+
+struct viewer *create_viewer(int fd, SDL_Renderer *renderer) {
+	struct viewer *v = calloc(1, sizeof(struct viewer));
+	if (!v) return NULL;
+	v->fd = fd; v->renderer = renderer;
+	v->page_texture = SDL_CreateTexture(v->renderer,
+			SDL_PIXELFORMAT_RGBA32,
+			SDL_TEXTUREACCESS_STREAMING,
+			PAGE_WIDTH, PAGE_HEIGHT);
+	if (!v->page_texture) {free(v); return NULL;}
+	return v;
+}
+
+void destroy_viewer(struct viewer *v) {
+	SDL_DestroyTexture(v->page_texture);
+	free(v);
+}
+
+static void render_page(SDL_Texture *tex, uint8_t *data) {
+	uint32_t *pixels; int pitch;
+	assert(SDL_LockTexture(tex, NULL, (void **) &pixels, &pitch) != -1);
+	if (data) {
+		for (int i = 0; i < PAGE_SIZE; i++) {
+			for (int j = 0; j < CHAR_BIT; j++) {
+				uint8_t bit = (data[i] >> j) & 1;
+				pixels[i * CHAR_BIT + j] = bit ? WHITE : BLACK;
+			}
+		}
+	} else {
+		for (int i = 0; i < PAGE_WIDTH * PAGE_HEIGHT; i++)
+			pixels[i] = GREY;
+	}
+	SDL_UnlockTexture(tex);
+}
+
+void render_pages(struct viewer *v,
+		int x, int y, int width, int height, double scale, bool refresh) {
+	int page_x = x / PAGE_WIDTH;
+	int page_y = y / PAGE_HEIGHT;
+
+	int offs_x = x % PAGE_WIDTH * scale;
+	int offs_y = y % PAGE_HEIGHT * scale;
+
+	int page_width = PAGE_WIDTH * scale;
+	int page_height = PAGE_HEIGHT * scale;
+
+	int view_width = width / page_width;
+	int view_height = height / page_height;
+
+	for (int draw_y = -1; draw_y <= view_height + 1; draw_y++) {
+		for (int draw_x = -1; draw_x <= view_width + 1; draw_x++) {
+			SDL_Rect src = {0, 0, PAGE_WIDTH, PAGE_HEIGHT};
+			SDL_Rect dest = {
+				draw_x * page_width - offs_x, draw_y * page_height - offs_y,
+				page_width, page_height
+			};
+			uintptr_t page = zorder(page_x + draw_x, page_y + draw_y);
+			bool success = read_page(v->fd, page, v->page_buffer) != -1;
+			// TODO: unless refresh is true, do not redraw if page unaltered
+			render_page(v->page_texture, success ? v->page_buffer : NULL);
+			SDL_RenderCopy(v->renderer, v->page_texture, &src, &dest);
+		}
+	}
+}
-- 
cgit v1.2.3