examples/to_json.rs: dump a program with JSON representation

Note: this example needs an additional external crate (`json`).

Cargo.toml

@@ -30,3 +30,4 @@ libc = "0.2.0"
 
 byteorder = "0.5.3"
 elf = "0.0.10"
+json = "0.11.4"

examples/to_json.rs

@@ -0,0 +1,72 @@
+// Copyright 2017 Quentin Monnet <quentin.monnet@6wind.com>
+//
+// Licensed under the Apache License, Version 2.0 <http://www.apache.org/licenses/LICENSE-2.0> or
+// the MIT license <http://opensource.org/licenses/MIT>, at your option. This file may not be
+// copied, modified, or distributed except according to those terms.
+
+
+#[macro_use]
+extern crate json;
+
+extern crate rbpf;
+use rbpf::disassembler;
+
+fn to_json(prog: &std::vec::Vec<u8>) -> String {
+
+    let insns = disassembler::to_insn_vec(&prog);
+    let mut json_insns = vec![];
+    for insn in insns {
+        json_insns.push(object!(
+                "opc"  => format!("{:#x}", insn.opc), // => insn.opc,
+                "dst"  => format!("{:#x}", insn.dst), // => insn.dst,
+                "src"  => format!("{:#x}", insn.src), // => insn.src,
+                "off"  => format!("{:#x}", insn.off), // => insn.off,
+                // Warning: for imm we use a i64 instead of a i32 (to have correct values for
+                // `lddw` operation. If we print a number in the JSON this is not a problem, the
+                // internal i64 has the same value with extended sign on 32 most significant bytes.
+                // If we print the hexadecimal value as a string however, we want to cast as a i32
+                // to prevent all other instructions to print spurious `ffffffff` prefix if the
+                // number is negative. When values takes more than 32 bits with `lddw`, the cast
+                // has no effect and the complete value is printed anyway.
+                "imm"  => format!("{:#x}", insn.imm as i32), // => insn.imm,
+                "desc" => format!("{}",    insn.desc)
+            )
+        );
+    }
+    json::stringify_pretty(object!(
+        "size"  => json_insns.len(),
+        "insns" => json_insns
+        ), 4)
+}
+
+fn main() {
+    let prog = vec![
+        0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x79, 0x12, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x79, 0x11, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0xbf, 0x13, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x07, 0x03, 0x00, 0x00, 0x36, 0x00, 0x00, 0x00,
+        0x2d, 0x23, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x69, 0x12, 0x0c, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x55, 0x02, 0x10, 0x00, 0x08, 0x00, 0x00, 0x00,
+        0x71, 0x12, 0x17, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x55, 0x02, 0x0e, 0x00, 0x06, 0x00, 0x00, 0x00,
+        0x18, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x79, 0x11, 0x22, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0xbf, 0x12, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x57, 0x02, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00,
+        0x15, 0x02, 0x08, 0x00, 0x99, 0x99, 0x00, 0x00,
+        0x18, 0x02, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x5f, 0x21, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0xb7, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff,
+        0x18, 0x02, 0x00, 0x00, 0x00, 0x00, 0x99, 0x99,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x1d, 0x21, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0xb7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x95, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+    ];
+
+    println!("{}", to_json(&prog));
+}