Merge pull request #1 from byte911/main

Add 02-01 Sha256

examples/src/01-01.zig

@@ -3,16 +3,18 @@ const fs = std.fs;
 const print = std.debug.print;
 
 pub fn main() !void {
-    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
-    defer arena.deinit();
-    const allocator = arena.allocator();
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    const allocator = gpa.allocator();
 
     const file = try fs.cwd().openFile("build.zig", .{});
     defer file.close();
 
     const rdr = file.reader();
     var line_no: usize = 0;
     while (try rdr.readUntilDelimiterOrEofAlloc(allocator, '\n', 4096)) |line| {
+        defer allocator.free(line);
+
         line_no += 1;
         print("{d}--{s}\n", .{ line_no, line });
     }

examples/src/02-01.zig

@@ -0,0 +1,30 @@
+const std = @import("std");
+const fs = std.fs;
+const print = std.debug.print;
+const Sha256 = std.crypto.hash.sha2.Sha256;
+
+fn sha256_digest(
+    allocator: std.mem.Allocator,
+    file: fs.File,
+) ![Sha256.digest_length]u8 {
+    const md = try file.metadata();
+    const size = md.size();
+    const bytes = try file.reader().readAllAlloc(allocator, size);
+    defer allocator.free(bytes);
+
+    var out: [Sha256.digest_length]u8 = undefined;
+    Sha256.hash(bytes, &out, .{});
+    return out;
+}
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    const allocator = gpa.allocator();
+
+    const file = try fs.cwd().openFile("build.zig", .{});
+    defer file.close();
+
+    const digest = try sha256_digest(allocator, file);
+    print("SHA-256 digest is {s}", .{std.fmt.fmtSliceHexLower(&digest)});
+}

src/01-01-read-file-line-by-line.md

@@ -9,6 +9,8 @@ There is a Reader type in Zig, which provides various methods to read file.
     const rdr = file.reader();
     var line_no: usize = 0;
     while (try rdr.readUntilDelimiterOrEofAlloc(allocator, '\n', 4096)) |line| {
+        defer allocator.free(line);
+
         line_no += 1;
         print("{d}--{s}\n", .{ line_no, line });
     }

src/02-01-sha-digest.md

@@ -0,0 +1,36 @@
+## Calculate SHA-256 digest of a file
+
+There are many crypto algorithm implementations in std, `sha256`, `md5` are supported out of box.
+
+```zig
+const std = @import("std");
+const fs = std.fs;
+const print = std.debug.print;
+const Sha256 = std.crypto.hash.sha2.Sha256;
+
+fn sha256_digest(
+    allocator: std.mem.Allocator,
+    file: fs.File,
+) ![Sha256.digest_length]u8 {
+    const md = try file.metadata();
+    const size = md.size();
+    const bytes = try file.reader().readAllAlloc(allocator, size);
+    defer allocator.free(bytes);
+
+    var out: [Sha256.digest_length]u8 = undefined;
+    Sha256.hash(bytes, &out, .{});
+    return out;
+}
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    const allocator = gpa.allocator();
+
+    const file = try fs.cwd().openFile("build.zig", .{});
+    defer file.close();
+
+    const digest = try sha256_digest(allocator, file);
+    print("SHA-256 digest is {s}", .{std.fmt.fmtSliceHexLower(&digest)});
+}
+```

src/SUMMARY.md

@@ -5,3 +5,6 @@
 - [File System]()
   - [Read file line by line](./01-01-read-file-line-by-line.md)
   - [Mmap file](./01-02-mmap-file.md)
+
+- [Cryptography]()
+  - [Calculate SHA-256 digest of a file](./02-01-sha-digest.md)