From 7c1bd03a71cccfcf48e79d241787021b0de98e73 Mon Sep 17 00:00:00 2001
From: hachem <im@hachem.wtf>
Date: Sun, 4 Oct 2026 02:02:15 +0200
Subject: feat: add more user programs

---
 user/hexview.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 user/hexview.c

(limited to 'user/hexview.c')

diff --git a/user/hexview.c b/user/hexview.c
new file mode 100644
index 0000000..f2425e1
--- /dev/null
+++ b/user/hexview.c
@@ -0,0 +1,91 @@
+// hexview, a ring 3 program that dumps a file from the revel fs. nav is n/p/q
+// since the keyboard only gives us decoded ascii, no arrow keys yet
+
+#include "user.h"
+
+static const char HEX[] = "0123456789abcdef";
+
+static void put_hex8(unsigned char byte)
+{
+    char digits[2] = { HEX[byte >> 4], HEX[byte & 15] };
+    sys_write(digits, 2);
+}
+
+static void put_hex32(unsigned long value)
+{
+    char digits[8];
+    for (int nibble = 0; nibble < 8; nibble++)
+        digits[nibble] = HEX[(value >> ((7 - nibble) * 4)) & 15];
+    sys_write(digits, 8);
+}
+
+#define PAGE 256
+#define COLS 16
+
+void _start(void)
+{
+    put("hexview, type a filename\nfile: ");
+    char name[64];
+    read_line(name, 64);
+    put("\n");
+
+    long size = sys_fs_size(name);
+    if (size < 0)
+    {
+        put("no such file\n");
+        sys_exit(1);
+    }
+
+    unsigned long offset = 0;
+    char buffer[PAGE];
+    for (;;)
+    {
+        long count = sys_fs_read(name, offset, buffer, PAGE);
+
+        put("--- ");
+        put(name);
+        put(" @ 0x");
+        put_hex32(offset);
+        put(" / 0x");
+        put_hex32((unsigned long)size);
+        put(" ---\n");
+
+        for (long row = 0; row < count; row += COLS)
+        {
+            put_hex32(offset + (unsigned long)row);
+            put(": ");
+            for (int column = 0; column < COLS; column++)
+            {
+                if (row + column < count)
+                {
+                    put_hex8((unsigned char)buffer[row + column]);
+                    sys_write(" ", 1);
+                }
+                else
+                    put("   ");
+            }
+            put(" ");
+            for (int column = 0; column < COLS && row + column < count; column++)
+            {
+                char character = buffer[row + column];
+                if (character >= 32 && character < 127)
+                    sys_write(&character, 1);
+                else
+                    sys_write(".", 1);
+            }
+            put("\n");
+        }
+
+        put("[n]ext [p]rev [q]uit > ");
+        char key = (char)sys_read();
+        put("\n");
+        if (key == 'q')
+            break;
+        if (key == 'n' && offset + PAGE < (unsigned long)size)
+            offset += PAGE;
+        if (key == 'p' && offset >= PAGE)
+            offset -= PAGE;
+    }
+
+    sys_exit(0);
+}
-- 
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