chore(users/Profpatsch): move cdbListToNetencode out of the blog r/3043

It’s a small tool that I’ve used before but not anymore, but since it
has a few helpers for dealing with cdb stuff, I’m gonna keep it around
for now I guess.

Change-Id: I83c62fa2194113d021414708b0906350b3f2a222
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3283
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

1 files changed, 91 insertions, 0 deletions

diff --git a/users/Profpatsch/cdb.nix b/users/Profpatsch/cdb.nix
new file mode 100644
index 0000000000..8cfaa3ea7a
--- /dev/null
+++ b/users/Profpatsch/cdb.nix
@@ -0,0 +1,91 @@
+{ depot, pkgs, ... }:
+
+let
+  cdbListToNetencode = depot.nix.writers.rustSimple {
+    name = "cdb-list-to-netencode";
+    dependencies = [
+      depot.third_party.rust-crates.nom
+      depot.users.Profpatsch.execline.exec-helpers
+      depot.users.Profpatsch.netencode.netencode-rs
+    ];
+  } ''
+    extern crate nom;
+    extern crate exec_helpers;
+    extern crate netencode;
+    use std::collections::HashMap;
+    use std::io::BufRead;
+    use nom::{IResult};
+    use nom::sequence::{tuple};
+    use nom::bytes::complete::{tag, take};
+    use nom::character::complete::{digit1, char};
+    use nom::error::{context, ErrorKind, ParseError};
+    use nom::combinator::{map_res};
+    use netencode::{T, Tag};
+
+    fn usize_t(s: &[u8]) -> IResult<&[u8], usize> {
+        context(
+            "usize",
+            map_res(
+                map_res(digit1, |n| std::str::from_utf8(n)),
+                |s| s.parse::<usize>())
+        )(s)
+    }
+
+    fn parse_cdb_record(s: &[u8]) -> IResult<&[u8], (&[u8], &[u8])> {
+        let (s, (_, klen, _, vlen, _)) = tuple((
+            char('+'),
+            usize_t,
+            char(','),
+            usize_t,
+            char(':')
+        ))(s)?;
+        let (s, (key, _, val)) = tuple((
+            take(klen),
+            tag("->"),
+            take(vlen),
+        ))(s)?;
+        Ok((s, (key, val)))
+    }
+
+    fn main() {
+        let mut res = vec![];
+        let stdin = std::io::stdin();
+        let mut lines = stdin.lock().split(b'\n');
+        loop {
+            match lines.next() {
+                None => exec_helpers::die_user_error("cdb-list-to-netencode", "stdin ended but we didn’t receive the empty line to signify the end of the cdbdump input!"),
+                Some(Err(err)) => exec_helpers::die_temporary("cdb-list-to-netencode", format!("could not read from stdin: {}", err)),
+                Some(Ok(line)) =>
+                    if &line == b"" {
+                        // the cdbdump input ends after an empty line (double \n)
+                        break;
+                    } else {
+                        match parse_cdb_record(&line) {
+                            Ok((b"", (key, val))) => {
+                                let (key, val) = match
+                                    std::str::from_utf8(key)
+                                    .and_then(|k| std::str::from_utf8(val).map(|v| (k, v))) {
+                                    Ok((key, val)) => (key.to_owned(), val.to_owned()),
+                                    Err(err) => exec_helpers::die_user_error("cdb-list-to-netencode", format!("cannot decode line {:?}, we only support utf8-encoded key/values pairs for now: {}", String::from_utf8_lossy(&line), err)),
+                                };
+                                let _ = res.push((key, val));
+                            },
+                            Ok((rest, _)) => exec_helpers::die_user_error("cdb-list-to-netencode", format!("could not decode record line {:?}, had some trailing bytes", String::from_utf8_lossy(&line))),
+                            Err(err) => exec_helpers::die_user_error("cdb-list-to-netencode", format!("could not decode record line {:?}: {:?}", String::from_utf8_lossy(&line), err)),
+                        }
+                    }
+            }
+        }
+        let list = T::List(res.into_iter().map(
+            |(k, v)| T::Record(vec![(String::from("key"), T::Text(k)), (String::from("val"), T::Text(v))].into_iter().collect())
+        ).collect());
+        netencode::encode(&mut std::io::stdout(), &list.to_u());
+    }
+
+  '';
+
+in {
+  inherit
+    cdbListToNetencode
+    ;
+}