From e5b21467c891fe9a2956358a38b496a5d9a174fc Mon Sep 17 00:00:00 2001
From: Meghan Denny <hello@nektro.net>
Date: Tue, 21 Nov 2023 10:38:15 -0800
Subject: [PATCH] add a lot more info to README

---
 README.md | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 100c0926dcd0686d0742a1a4e31cfbf6efb2eec3..7b2dcff608320cd4768b92be436dc19ceb4dbfdf 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ const std = @import("std");
 const tracer = @import("tracer");
 pub const build_options = @import("build_options");
 
-pub const tracer_impl = tracer.spall; // supports none, log, spall out of the box
+pub const tracer_impl = tracer.spall; // see 'Backends' section below
 
 pub fn main() !void {
     try tracer.init();
@@ -43,6 +43,23 @@ fn handler() void {
 exe_options.addOption(usize, "src_file_trimlen", std.fs.path.dirname(std.fs.path.dirname(@src().file).?).?.len);
 ```
 
+## Backends
+
+- `none` this is the default and causes tracing calls to become a no-op so that `tracer` can be added to libraries transparently
+- `log` uses `std.log` to print on function entrance.
+- `chrome` writes a json file in the `chrome://tracing` format described [here](https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview) and [here](https://www.chromium.org/developers/how-tos/trace-event-profiling-tool/).
+- `spall` writes a binary file compatible with the [Spall](https://gravitymoth.com/spall/) profiler.
+- more? feel free to open an issue with requests!
+
+Any custom backend may also be used that defines the following functions:
+
+- `pub fn init() !void`
+- `pub fn deinit() void`
+- `pub fn init_thread() !void`
+- `pub fn deinit_thread() void`
+- `pub inline fn trace_begin(ctx: tracer.Ctx, comptime ifmt: []const u8, iargs: anytype) void`
+- `pub inline fn trace_end(ctx: tracer.Ctx) void`
+
 ## License
 
 MIT
-- 
2.54.0