From e92459156c2f74de648566ca7acde3833de33425 Mon Sep 17 00:00:00 2001
From: Martin Ashby <martin@ashbysoft.com>
Date: Sat, 11 Nov 2023 20:47:46 +0000
Subject: Include ownership info on BValue.

It's a bit cumbersome, but it caters for the two situations: a. parsing
from a stream where strings must be copied into the structure and owned,
and b. constructing from application code where strings must _not_ be
freed. Either way, the base structures (array list, hash map) are always
owned and must be freed.

Add method and test for info hash
---
 src/metainfo.zig | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

(limited to 'src/metainfo.zig')

diff --git a/src/metainfo.zig b/src/metainfo.zig
index a202b0e..31b14b7 100644
--- a/src/metainfo.zig
+++ b/src/metainfo.zig
@@ -9,10 +9,14 @@ pub const Info = struct {
         name: []const u8,
         length: u64,
         path: []const u8,
+        md5sum: ?[]const u8 = null,
     };
+
     piece_length: u64,
     pieces: []const u8,
     files: []File,
+    private: ?bool,
+
     pub fn parse(a: std.mem.Allocator, b: bencode.BValue) Error!Info {
         var d = b.asDict() catch return error.Malformatted;
         const pl = d.get("piece length") orelse return error.Malformatted;
@@ -27,33 +31,89 @@ pub const Info = struct {
                 const fin = fd.get("name") orelse return error.Malformatted;
                 const fl = fd.get("length") orelse return error.Malformatted;
                 const fp = fd.get("path") orelse return error.Malformatted;
+                var fm: ?[]const u8 = null;
+                if (fd.get("md5sum")) |md5| {
+                    fm = md5.asString() catch return error.Malformatted;
+                }
                 try files.append(.{
                     .name = fin.asString() catch return error.Malformatted,
                     .length = fl.asInt(u64) catch return error.Malformatted,
                     .path = fp.asString() catch return error.Malformatted,
+                    .md5sum = fm,
                 });
             }
         } else {
             // single-file mode
             const fin = d.get("name") orelse return error.Malformatted;
             const fl = d.get("length") orelse return error.Malformatted;
+            var fm: ?[]const u8 = null;
+            if (d.get("md5sum")) |md5| {
+                fm = md5.asString() catch return error.Malformatted;
+            }
             try files.append(.{
                 .name = fin.asString() catch return error.Malformatted,
                 .length = fl.asInt(u64) catch return error.Malformatted,
                 .path = fin.asString() catch return error.Malformatted, // just use the file name as path
+                .md5sum = fm,
             });
         }
 
+        var priv: ?bool = null;
+        if (d.get("private")) |pr| {
+            const pri = pr.asInt(u1) catch return error.Malformatted;
+            priv = pri == 1;
+        }
         return .{
             .piece_length = pl.asInt(u64) catch return error.Malformatted,
             .pieces = pp.asString() catch return error.Malformatted,
             .files = try files.toOwnedSlice(),
+            .private = priv,
         };
     }
 
+    pub fn encode(self: Info, a: std.mem.Allocator) Error!bencode.BValue {
+        var r: bencode.BValue = .{ .dict = .{ .dict = std.StringArrayHashMap(bencode.BValue).init(a) } };
+        errdefer r.deinit(a);
+        if (self.files.len > 1) {
+            @panic("TODO");
+        } else if (self.files.len == 1) {
+            const f = self.files[0];
+            const l = std.math.cast(i64, f.length) orelse return error.Malformatted;
+            try r.dict.dict.put("length", .{ .int = l });
+            try r.dict.dict.put("name", .{ .string = .{ .string = f.name } });
+            if (f.md5sum) |fm| {
+                try r.dict.dict.put("md5sum", .{ .string = .{ .string = fm } });
+            }
+        } else {
+            return error.Malformatted;
+        }
+
+        try r.dict.dict.put("pieces", .{ .string = .{ .string = self.pieces } });
+        const pl = std.math.cast(i64, self.piece_length) orelse return error.Malformatted;
+        try r.dict.dict.put("piece length", .{ .int = pl });
+        if (self.private) |pr| {
+            const pri: i64 = if (pr) 1 else 0;
+            try r.dict.dict.put("private", .{ .int = pri });
+        }
+
+        return r;
+    }
+
     pub fn deinit(self: *Info, a: std.mem.Allocator) void {
         a.free(self.files);
     }
+
+    const info_hash_len = 40;
+    pub fn hash(self: Info, a: std.mem.Allocator) ![info_hash_len]u8 {
+        var b = try self.encode(a);
+        defer b.deinit(a);
+        var sha1 = std.crypto.hash.Sha1.init(.{});
+        var w = sha1.writer();
+        try b.bencode(w);
+        var buf = [_]u8{0} ** info_hash_len;
+        _ = std.fmt.bufPrint(&buf, "{}", .{std.fmt.fmtSliceHexLower(&sha1.finalResult())}) catch unreachable;
+        return buf;
+    }
 };
 
 info: Info,
@@ -70,6 +130,14 @@ pub fn parse(a: std.mem.Allocator, b: bencode.BValue) Error!MetaInfo {
     };
 }
 
+pub fn encode(self: MetaInfo, a: std.mem.Allocator) !bencode.BValue {
+    var d: bencode.BValue = .{ .dict = .{ .dict = std.StringArrayHashMap(bencode.BValue).init(a) } };
+    errdefer d.deinit(a);
+    try d.put("announce", .{ .string = .{ .string = self.announce } });
+    try d.put("info", try self.info.encode(a));
+    return d;
+}
+
 pub fn deinit(self: *MetaInfo, a: std.mem.Allocator) void {
     self.info.deinit(a);
 }
@@ -85,3 +153,14 @@ test "sample" {
     try std.testing.expectEqual(@as(usize, 1), mi.info.files.len);
     try std.testing.expectEqualStrings("sample.txt", mi.info.files[0].name);
 }
+
+test "info hash" {
+    const a = std.testing.allocator;
+    const sample_str = @embedFile("sample.torrent");
+    var b = try bencode.bdecodeBuf(a, sample_str);
+    defer b.deinit(a);
+    var mi = try MetaInfo.parse(a, b);
+    defer mi.deinit(a);
+    const hash = try mi.info.hash(a);
+    try std.testing.expectEqualStrings("d69f91e6b2ae4c542468d1073a71d4ea13879a7f", &hash);
+}
-- 
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