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refactor(ledger): rename ret to returnOutput and add docs
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@dnut
dnut committed Nov 5, 2024
1 parent 98f4d11 commit f086a56
Showing 1 changed file with 63 additions and 25 deletions.
88 changes: 63 additions & 25 deletions src/ledger/database/lmdb.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -27,12 +27,12 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
const owned_path = try allocator.dupeZ(u8, path);

// create and open the database
const env = try ret(c.mdb_env_create, .{});
const env = try returnOutput(c.mdb_env_create, .{});
try maybeError(c.mdb_env_set_maxdbs(env, column_families.len));
try maybeError(c.mdb_env_open(env, owned_path.ptr, 0, 0o700));

// begin transaction to create column families aka "databases" in lmdb
const txn = try ret(c.mdb_txn_begin, .{ env, null, 0 });
const txn = try returnOutput(c.mdb_txn_begin, .{ env, null, 0 });
errdefer c.mdb_txn_abort(txn);

// allocate cf handles
Expand All @@ -42,7 +42,7 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
// save cf handles
inline for (column_families, 0..) |cf, i| {
// open cf/database, creating if necessary
dbis[i] = try ret(c.mdb_dbi_open, .{ txn, cf.name.ptr, c.MDB_CREATE });
dbis[i] = try returnOutput(c.mdb_dbi_open, .{ txn, cf.name.ptr, c.MDB_CREATE });
}

// persist column families
Expand All @@ -66,10 +66,10 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
}

pub fn count(self: *Self, comptime cf: ColumnFamily) LmdbOrAllocatorError!u64 {
const txn = try ret(c.mdb_txn_begin, .{ self.env, null, c.MDB_RDONLY });
const txn = try returnOutput(c.mdb_txn_begin, .{ self.env, null, c.MDB_RDONLY });
defer c.mdb_txn_abort(txn);

const stat = try ret(c.mdb_stat, .{ txn, self.dbi(cf) });
const stat = try returnOutput(c.mdb_stat, .{ txn, self.dbi(cf) });

return stat.ms_entries;
}
Expand All @@ -85,7 +85,7 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
const val_bytes = try value_serializer.serializeToRef(self.allocator, value);
defer val_bytes.deinit();

const txn = try ret(c.mdb_txn_begin, .{ self.env, null, 0 });
const txn = try returnOutput(c.mdb_txn_begin, .{ self.env, null, 0 });
errdefer c.mdb_txn_abort(txn);

var key_val = toVal(key_bytes.data);
Expand All @@ -104,10 +104,10 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
defer key_bytes.deinit();
var key_val = toVal(key_bytes.data);

const txn = try ret(c.mdb_txn_begin, .{ self.env, null, c.MDB_RDONLY });
const txn = try returnOutput(c.mdb_txn_begin, .{ self.env, null, c.MDB_RDONLY });
defer c.mdb_txn_abort(txn);

const value = ret(c.mdb_get, .{ txn, self.dbi(cf), &key_val }) catch |e| switch (e) {
const value = returnOutput(c.mdb_get, .{ txn, self.dbi(cf), &key_val }) catch |e| switch (e) {
error.MDB_NOTFOUND => return null,
else => return e,
};
Expand All @@ -120,10 +120,10 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
defer key_bytes.deinit();
var key_val = toVal(key_bytes.data);

const txn = try ret(c.mdb_txn_begin, .{ self.env, null, c.MDB_RDONLY });
const txn = try returnOutput(c.mdb_txn_begin, .{ self.env, null, c.MDB_RDONLY });
errdefer c.mdb_txn_abort(txn);

const item = ret(c.mdb_get, .{ txn, self.dbi(cf), &key_val }) catch |e| switch (e) {
const item = returnOutput(c.mdb_get, .{ txn, self.dbi(cf), &key_val }) catch |e| switch (e) {
error.MDB_NOTFOUND => return null,
else => return e,
};
Expand All @@ -144,7 +144,7 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
var key_val = toVal(key_bytes.data);
var val_val: c.MDB_val = undefined;

const txn = try ret(c.mdb_txn_begin, .{ self.env, null, 0 });
const txn = try returnOutput(c.mdb_txn_begin, .{ self.env, null, 0 });
errdefer c.mdb_txn_abort(txn);

maybeError(c.mdb_del(txn, self.dbi(cf), &key_val, &val_val)) catch |e| switch (e) {
Expand Down Expand Up @@ -172,7 +172,7 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
executed.* = false;
return .{
.allocator = self.allocator,
.txn = try ret(c.mdb_txn_begin, .{ self.env, null, 0 }),
.txn = try returnOutput(c.mdb_txn_begin, .{ self.env, null, 0 }),
.dbis = self.dbis,
.executed = executed,
};
Expand Down Expand Up @@ -246,7 +246,7 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
const end_bytes = try key_serializer.serializeToRef(self.allocator, end);
defer end_bytes.deinit();

const cursor = try ret(c.mdb_cursor_open, .{ self.txn, self.dbi(cf) });
const cursor = try returnOutput(c.mdb_cursor_open, .{ self.txn, self.dbi(cf) });
defer c.mdb_cursor_close(cursor);

var key, _ = if (try cursorGet(cursor, start_bytes.data, .set_range)) |kv|
Expand All @@ -273,10 +273,10 @@ pub fn LMDB(comptime column_families: []const ColumnFamily) type {
null;
defer if (maybe_start_bytes) |sb| sb.deinit();

const txn = try ret(c.mdb_txn_begin, .{ self.env, null, 0 });
const txn = try returnOutput(c.mdb_txn_begin, .{ self.env, null, 0 });
errdefer c.mdb_txn_abort(txn);

const cursor = try ret(c.mdb_cursor_open, .{ txn, self.dbi(cf) });
const cursor = try returnOutput(c.mdb_cursor_open, .{ txn, self.dbi(cf) });
errdefer c.mdb_cursor_close(cursor);

var start_operation: CursorRelativeOperation = .get_current;
Expand Down Expand Up @@ -398,29 +398,67 @@ fn resetTxnFree(ctx: *anyopaque, _: []u8, _: u8, _: usize) void {
c.mdb_txn_abort(txn);
}

fn ret(constructor: anytype, args: anytype) LmdbError!TypeToCreate(constructor) {
const Intermediate = IntermediateType(constructor);
var maybe: IntermediateType(constructor) = switch (@typeInfo(Intermediate)) {
/// Call an LMDB function and return its combined output as an error union.
///
/// This converts parameter-based outputs into return values, and converts error
/// code integers into zig errors.
///
/// LMDB functions only return integers representing an error code. If the
/// function actually needs to provide more data as an output, the caller needs
/// to pass in a pointer as the final argument to the function. LMDB will write
/// the output data to that pointer. This makes LMDB cumbersome to use because it
/// requires you to have a few extra lines of code every time you call an LMDB
/// function that has any outputs. This function implements this process for you,
/// so you can get the output data as a normal return value.
///
/// To use it, pass in the LMDB function you'd like to call, and all of the
/// arguments for that function *except the last*. The last argument is for the
/// output, and will be provided by this function.
///
/// Without `returnOutput`:
/// ```zig
/// const maybe_env: ?*MDB_env = null;
/// try maybeError(c.mdb_env_create(&maybe_env));
/// const env = maybe_env.?;
/// ```
///
/// With `returnOutput`:
/// ```zig
/// const env = try returnOutput(c.mdb_env_create, .{});
/// ```
fn returnOutput(fn_with_output: anytype, args: anytype) LmdbError!OutputType(fn_with_output) {
// create a local variable to hold the function's output.
const MaybeOutput = LastParamChild(fn_with_output);
var maybe_output: MaybeOutput = switch (@typeInfo(MaybeOutput)) {
.Optional => null,
.Int => 0,
else => undefined,
};
try maybeError(@call(.auto, constructor, args ++ .{&maybe}));
return switch (@typeInfo(Intermediate)) {
.Optional => maybe.?,
else => maybe,

// call the function, passing a pointer to the output variable.
// check the return code, and return an error if there was an error.
try maybeError(@call(.auto, fn_with_output, args ++ .{&maybe_output}));

// return the output value, unwrapping the optional if needed.
return switch (@typeInfo(MaybeOutput)) {
.Optional => maybe_output.?,
else => maybe_output,
};
}

fn TypeToCreate(function: anytype) type {
const InnerType = IntermediateType(function);
/// For an LMDB function that provides its output by writing to a pointer, this
/// is the data type of the output.
fn OutputType(fn_with_output: anytype) type {
const InnerType = LastParamChild(fn_with_output);
return switch (@typeInfo(InnerType)) {
.Optional => |o| o.child,
else => InnerType,
};
}

fn IntermediateType(function: anytype) type {
/// Returns the child type of the last parameter of a function,
/// assuming that parameter is a pointer.
fn LastParamChild(function: anytype) type {
const params = @typeInfo(@TypeOf(function)).Fn.params;
return @typeInfo(params[params.len - 1].type.?).Pointer.child;
}
Expand Down

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