code review 7312072: go.talks/pkg/present: replace direct file system access...

pkg/present/code.go

Index: pkg/present/code.go 
=================================================================== 
--- a/pkg/present/code.go 
+++ b/pkg/present/code.go 
@@ -7,7 +7,6 @@ 
 import ( 
	"fmt" 
	"html/template" 
-	"io/ioutil" 
	"log" 
	"path/filepath" 
	"regexp" 
@@ -42,7 +41,7 @@ 
 var highlightRE = regexp.MustCompile(`\s+HL([a-zA-Z0-9_]+)?$`) 
 var codeRE = regexp.MustCompile(`\.(code|play)\s+([^\s]+)(\s+)?(.*)?$`) 
 
-func parseCode(sourceFile string, sourceLine int, cmd string) (Elem, error) { 
+func parseCode(ctx *Context, sourceFile string, sourceLine int, cmd string) (Elem, error) { 
	cmd = strings.TrimSpace(cmd) 
 
	// Pull off the HL, if any, from the end of the input line. 
@@ -68,7 +67,7 @@ 
 
	// Read in code file and (optionally) match address. 
	filename := filepath.Join(filepath.Dir(sourceFile), file) 
-	textBytes, err := ioutil.ReadFile(filename) 
+	textBytes, err := ctx.ReadFile(filename) 
	if err != nil { 
	return nil, fmt.Errorf("%s:%d: %v", sourceFile, sourceLine, err) 
	} 
@@ -168,8 +167,8 @@ 
 } 
 
 // oneLine returns the single line generated by a two-argument code invocation. 
-func oneLine(file, text string, arg interface{}) (line, before, after string, err error) { 
-	contentBytes, err := ioutil.ReadFile(file) 
+func oneLine(ctx *Context, file, text string, arg interface{}) (line, before, after string, err error) { 
+	contentBytes, err := ctx.ReadFile(file) 
	if err != nil { 
	return "", "", "", err 
	} 
@@ -192,8 +191,8 @@ 
 } 
 
 // multipleLines returns the text generated by a three-argument code invocation. 
-func multipleLines(file string, arg1, arg2 interface{}) (line, before, after string, err error) { 
-	contentBytes, err := ioutil.ReadFile(file) 
+func multipleLines(ctx *Context, file string, arg1, arg2 interface{}) (line, before, after string, err error) { 
+	contentBytes, err := ctx.ReadFile(file) 
	lines := strings.SplitAfter(string(contentBytes), "\n") 
	if err != nil { 
	return "", "", "", err