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const std = @import("std");
const pq = @cImport(
@cInclude("libpq-fe.h"),
);
pub const PqError = error{PqError};
// libpq wrapper
// later, this could be a pure-zig client implementation
pub const Db = struct {
c_conn: *pq.PGconn,
pub fn init(connect_url: [:0]const u8) !Db {
if (pq.PQisthreadsafe() == 0) {
std.log.err("PQisthreadsafe returned 0, can't use libpq in this program", .{});
return PqError.PqError;
}
const maybe_conn: ?*pq.PGconn = pq.PQconnectdb(connect_url);
if (maybe_conn == null) {
std.log.err("PQconnectdb returned null", .{});
return PqError.PqError;
}
if (pq.PQstatus(maybe_conn) == pq.CONNECTION_BAD) {
std.log.err("PQstatus returned CONNECTION_BAD: {s}", .{pq.PQerrorMessage(maybe_conn)});
return PqError.PqError;
} else if (pq.PQstatus(maybe_conn) != pq.CONNECTION_OK) {
std.log.err("PQstatus returned unknown status {}: {s}", .{ pq.PQstatus(maybe_conn), pq.PQerrorMessage(maybe_conn) });
return PqError.PqError;
}
return Db{
.c_conn = maybe_conn.?,
};
}
pub fn deinit(self: Db) void {
pq.PQfinish(self.c_conn);
}
pub fn exec(self: Db, query: [:0]const u8) !void {
const res: ?*pq.PGresult = pq.PQexec(self.c_conn, query);
defer pq.PQclear(res);
const est: pq.ExecStatusType = pq.PQresultStatus(res);
if (est != pq.PGRES_COMMAND_OK) {
std.log.err("PQexec error code {} message {s}", .{ est, pq.PQerrorMessage(self.c_conn) });
return PqError.PqError;
}
}
pub fn prepare_statement(self: Db, allocator: std.mem.Allocator, query: [:0]const u8) PqError!Stmt {
return Stmt{
.db = self,
.aa = std.heap.ArenaAllocator.init(allocator),
.query = query,
};
}
};
pub const Stmt = struct {
const MAX_PARAMS = 128;
db: Db,
query: [:0]const u8,
aa: std.heap.ArenaAllocator,
n_params: usize = 0,
param_values: [MAX_PARAMS][*c]const u8 = undefined,
did_exec: bool = false,
c_res: ?*pq.PGresult = null,
res_index: c_int = -1,
n_tuples: c_int = -1,
n_fields: c_int = -1,
pub fn deinit(self: *Stmt) void {
self.aa.deinit();
if (self.c_res != null) {
pq.PQclear(self.c_res);
}
}
pub fn step(self: *Stmt) !bool {
if (!self.did_exec) {
self.did_exec = true;
self.c_res = pq.PQexecParams(self.db.c_conn, self.query, @as(c_int, @intCast(self.n_params)), null, &self.param_values, null, null, 0);
const rs = pq.PQresultStatus(self.c_res);
if (rs != pq.PGRES_TUPLES_OK and rs != pq.PGRES_SINGLE_TUPLE and rs != pq.PGRES_COMMAND_OK) {
std.log.err("PQresultStatus {} error: {s}", .{ rs, pq.PQerrorMessage(self.db.c_conn) });
return PqError.PqError;
}
self.n_tuples = pq.PQntuples(self.c_res);
self.n_fields = pq.PQnfields(self.c_res);
}
self.res_index = self.res_index + 1;
return self.res_index < self.n_tuples;
}
pub fn read_column(self: Stmt, idx: c_int, comptime T: type) !T {
const value_c: [*c]u8 = pq.PQgetvalue(self.c_res, self.res_index, idx);
const value: []const u8 = std.mem.sliceTo(value_c, 0);
return switch (@typeInfo(T)) {
.Int => std.fmt.parseInt(T, value, 10),
.Pointer => |ptrinfo| blk: {
if (ptrinfo.child != u8) {
@compileError("pointer type []const u8 only is supported in read_column");
}
if (ptrinfo.size != .Slice) {
@compileError("pointer type []const u8 only is supported in read_column");
}
break :blk value;
},
else => @compileError("unhandled type " ++ @tagName(@typeInfo(T)) ++ " in read_column"),
};
}
pub fn read_columnN(self: Stmt, name: [:0]const u8, comptime T: type) !T {
const idx = pq.PQfnumber(self.c_res, name.ptr);
if (idx == -1) {
std.log.err("read_columnN ColumnNotFound [{s}]", .{name});
return error.ColumnNotFound;
}
return read_column(self, idx, T);
}
pub fn bind(self: *Stmt, idx: usize, t: anytype) !void {
const T = @TypeOf(t);
const value: [:0]const u8 = switch (@typeInfo(T)) {
.Pointer => try std.fmt.allocPrintZ(self.aa.allocator(), "{s}", .{t}),
.Int => try std.fmt.allocPrintZ(self.aa.allocator(), "{d}", .{t}),
else => @compileError("unhandled type " ++ @tagName(@typeInfo(T) ++ " in bind")),
};
self.param_values[idx] = value.ptr;
self.n_params = @max(self.n_params, idx + 1);
}
pub fn read_struct(self: Stmt, comptime T: type) !T {
const ti = @typeInfo(T);
var t: T = undefined;
inline for (ti.Struct.fields) |field| {
const name: [:0]const u8 = &addZ(field.name.len, field.name[0..].*);
const val = try self.read_columnN(name, field.type);
@field(t, field.name) = val;
}
return t;
}
};
// https://github.com/ziglang/zig/issues/16116
pub fn addZ(comptime length: usize, value: [length]u8) [length:0]u8 {
var terminated_value: [length:0]u8 = undefined;
terminated_value[length] = 0;
@memcpy(&terminated_value, &value);
return terminated_value;
}
test "connect" {
var db = try Db.init("postgresql://localhost/comments");
db.deinit();
}
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