small fixes / documentation

mysql.lua

@@ -1,4 +1,10 @@
---mysql ffi binding (Cosmin Apreutesei, public domain). supports mysql Connector/C 6.1. based on mySQL 5.7 manual.
+
+--mySQL client library ffi binding.
+--Written by Cosmin Apreutesei. Public domain.
+
+--Supports mysql Connector/C 6.1.
+--Based on mySQL 5.7 manual.
+
 local ffi = require'ffi'
 local bit = require'bit'
 require'mysql_h'
@@ -22,24 +28,25 @@ end
 
 --error reporting
 
-local function myerror(mysql)
+local function myerror(mysql, stacklevel)
 	local err = cstring(C.mysql_error(mysql))
 	if not err then return end
-	error(string.format('mysql error: %s', err))
+	error(string.format('mysql error: %s', err), stacklevel or 3)
 end
 
 local function checkz(mysql, ret)
 	if ret == 0 then return end
-	myerror(mysql)
+	myerror(mysql, 4)
 end
 
 local function checkh(mysql, ret)
 	if ret ~= NULL then return ret end
-	myerror(mysql)
+	myerror(mysql, 4)
 end
 
 local function enum(e, prefix)
-	return assert(type(e) == 'string' and (prefix and C[prefix..e] or C[e]) or e, 'invalid enum value')
+	local v = type(e) == 'string' and (prefix and C[prefix..e] or C[e]) or e
+	return assert(v, 'invalid enum value')
 end
 
 --client library info
@@ -582,7 +589,7 @@ local function fetch_row(res, numeric, assoc, decode, field_count, fields, t)
 	local values = C.mysql_fetch_row(res)
 	if values == NULL then
 		if res.conn ~= NULL then --buffered read: check for errors
-			myerror(res.conn)
+			myerror(res.conn, 4)
 		end
 		return nil
 	end
@@ -694,25 +701,25 @@ end
 
 --prepared statements
 
-local function sterror(stmt)
+local function sterror(stmt, stacklevel)
 	local err = cstring(C.mysql_stmt_error(stmt))
 	if not err then return end
-	error(string.format('mysql error: %s', err))
+	error(string.format('mysql error: %s', err), stacklevel or 3)
 end
 
 local function stcheckz(stmt, ret)
 	if ret == 0 then return end
-	sterror(stmt)
+	sterror(stmt, 4)
 end
 
 local function stcheckbool(stmt, ret)
 	if ret == 1 then return end
-	sterror(stmt)
+	sterror(stmt, 4)
 end
 
 local function stcheckh(stmt, ret)
 	if ret ~= NULL then return ret end
-	sterror(stmt)
+	sterror(stmt, 4)
 end
 
 function conn.prepare(mysql, query)
@@ -774,11 +781,12 @@ end
 
 function stmt.result_metadata(stmt)
 	local res = stcheckh(stmt, C.mysql_stmt_result_metadata(stmt))
-	return ffi.gc(res, C.mysql_free_result)
+	return res and ffi.gc(res, C.mysql_free_result)
 end
 
 function stmt.fields(stmt)
 	local res = stmt:result_metadata()
+	if not res then return nil end
 	local fields = res:fields()
 	return function()
 		local i, info = fields()
@@ -1183,6 +1191,7 @@ function stmt.bind_result_types(stmt, maxsize)
 	local types = {}
 	local field_count = stmt:field_count()
 	local res = stmt:result_metadata()
+	if not res then return nil end
 	for i=1,field_count do
 		local ftype, size, unsigned, decimals = res:field_type(i)
 		if ftype == 'decimal' then
@@ -1199,7 +1208,7 @@ function stmt.bind_result_types(stmt, maxsize)
 end
 
 function stmt.bind_params(stmt, ...)
-	local types = type(...) == 'string' and {...} or ... or {}
+	local types = type((...)) == 'string' and {...} or ... or {}
 	assert(stmt:param_count() == #types, 'wrong number of param types')
 	local bb = params_bind_buffer(types)
 	stcheckz(stmt, C.mysql_stmt_bind_param(stmt, bb.buffer))