- correct error handling throughout

- documentation, cleanups
- more options

R=r
OCL=19736
CL=19736

3 files changed, 150 insertions, 117 deletions

diff --git a/usr/gri/pretty/printer.go b/usr/gri/pretty/printer.go
index 3e364618a..cefabb66f 100644
--- a/usr/gri/pretty/printer.go
+++ b/usr/gri/pretty/printer.go
@@ -15,8 +15,8 @@ import OS "os"
 import TabWriter "tabwriter"
 
 var (
-	usetabs = Flag.Bool("usetabs", false, nil, "align with tabs instead of blanks");
 	tabwidth = Flag.Int("tabwidth", 4, nil, "tab width");
+	usetabs = Flag.Bool("usetabs", false, nil, "align with tabs instead of blanks");
 	comments = Flag.Bool("comments", false, nil, "enable printing of comments");
 )
 
@@ -604,7 +604,7 @@ func (P *Printer) Declaration(d *AST.Decl, parenthesized bool) {
 
 func (P *Printer) Program(p *AST.Program) {
 	// TODO should initialize all fields?
-	P.writer = TabWriter.MakeTabWriter(OS.Stdout, usetabs.BVal(), int(tabwidth.IVal()));
+	P.writer = TabWriter.New(OS.Stdout, int(tabwidth.IVal()), 1, usetabs.BVal());
 	
 	P.clist = p.comments;
 	P.cindex = 0;
diff --git a/usr/gri/pretty/tabwriter.go b/usr/gri/pretty/tabwriter.go
index 53a275514..58ae5ff1e 100644
--- a/usr/gri/pretty/tabwriter.go
+++ b/usr/gri/pretty/tabwriter.go
@@ -13,7 +13,7 @@ import (
 
 // ----------------------------------------------------------------------------
 // ByteArray
-// TODO move this into std lib eventually
+// TODO should use a ByteArray library eventually
 
 type ByteArray struct {
 	a *[]byte;
@@ -30,21 +30,6 @@ func (b *ByteArray) Clear() {
 }
 
 
-func (b *ByteArray) Len() int {
-	return len(b.a);
-}
-
-
-func (b *ByteArray) At(i int) byte {
-	return b.a[i];
-}
-
-
-func (b *ByteArray) Set(i int, x byte) {
-	b.a[i] = x;
-}
-
-
 func (b *ByteArray) Slice(i, j int) *[]byte {
 	return b.a[i : j];  // BUG should really be &b.a[i : j]
 }
@@ -76,27 +61,42 @@ func (b *ByteArray) Append(s *[]byte) {
 
 
 // ----------------------------------------------------------------------------
-// Implementation of flexible tab stops.
-
-// TabWriter is a representation for a list of lines consisting of
-// cells. A new cell is added for each Tab() call, and a new line
-// is added for each Newline() call.
+// Tabwriter is a filter implementing the IO.Write interface. It assumes
+// that the incoming bytes represent ASCII encoded text consisting of
+// lines of tab-separated "cells". Cells in adjacent lines constitute
+// a column. Tabwriter rewrites the incoming text such that all cells
+// in a column have the same width; thus it effectively aligns cells.
+// It does this by adding padding where necessary.
+//
+// Formatting can be controlled via parameters:
+//
+// tabwidth  the minimal with of a cell
+// padding   additional padding
+// usetabs   use tabs instead of blanks for padding
+//           (for correct-looking results, tabwidth must correspond
+//           to the tabwidth in the editor used to look at the result)
 //
-// The lines are formatted and printed such that all cells in a column
-// of adjacent cells have the same width (by adding padding). For more
-// details see: http://nickgravgaard.com/elastictabstops/index.html .
+// (See alse http://nickgravgaard.com/elastictabstops/index.html)
+
+// TODO Should support UTF-8
+// TODO Should probably implement a couple of trivial customization options
+//      such as arbitrary padding character, left/right alignment, and inde-
+//      pendant cell and tab width.
+
 
 export type TabWriter struct {
+	// TODO should not export any of the fields
 	// configuration
 	writer io.Write;
-	usetabs bool;
 	tabwidth int;
+	padding int;
+	usetabs bool;
 
 	// current state
 	buf ByteArray;  // the collected text w/o tabs and newlines
 	width int;  // width of last incomplete cell
 	lines array.Array;  // list of lines; each line is a list of cell widths
-	widths array.IntArray;  // list of column widths - (re-)used during formatting
+	widths array.IntArray;  // list of column widths - re-used during formatting
 }
 
 
@@ -105,15 +105,18 @@ func (b *TabWriter) AddLine() {
 }
 
 
-func (b *TabWriter) Init(writer io.Write, usetabs bool, tabwidth int) {
+func (b *TabWriter) Init(writer io.Write, tabwidth, padding int, usetabs bool) *TabWriter {
 	b.writer = writer;
-	b.usetabs = usetabs;
 	b.tabwidth = tabwidth;
+	b.padding = padding;
+	b.usetabs = usetabs;
 	
 	b.buf.Init(1024);
 	b.lines.Init(0);
 	b.widths.Init(0);
 	b.AddLine();  // the very first line
+	
+	return b;
 }
 
 
@@ -135,7 +138,7 @@ func (b *TabWriter) Dump() {
 		print("(", i, ") ");
 		for j := 0; j < line.Len(); j++ {
 			w := line.At(j);
-			print("[", string(b.buf.a[pos : pos + w]), "]");
+			print("[", string(b.buf.Slice(pos, pos + w)), "]");
 			pos += w;
 		}
 		print("\n");
@@ -144,59 +147,95 @@ func (b *TabWriter) Dump() {
 }
 
 
+func (b *TabWriter) Write0(buf *[]byte) *os.Error {
+	n, err := b.writer.Write(buf);
+	if n != len(buf) && err == nil {
+		err = os.EIO;
+	}
+	return err;
+}
+
+
 var Tabs = &[]byte{'\t', '\t', '\t', '\t', '\t', '\t', '\t', '\t'}
 var Blanks = &[]byte{' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '}
 var Newline = &[]byte{'\n'}
 
 
-func (b *TabWriter) Padding(textwidth, cellwidth int) {
-	n := cellwidth - textwidth;
+func (b *TabWriter) WritePadding(textw, cellw int) (err *os.Error) {
+	if b.usetabs {
+		// make cell width a multiple of tabwidth
+		cellw = ((cellw + b.tabwidth - 1) / b.tabwidth) * b.tabwidth;
+	}
+
+	n := cellw - textw;
 	if n < 0 {
 		panic("internal error");
 	}
+
+	padding := Blanks;
 	if b.usetabs {
-		if cellwidth % b.tabwidth != 0 {
-			panic("internal error");  // cellwidth should be a multiple of tabwidth
-		}
 		n = (n + b.tabwidth - 1) / b.tabwidth;
-		for n > len(Tabs) {
-			m, err := b.writer.Write(Tabs);
-			n -= len(Tabs);
-		}
-		m, err := b.writer.Write(Tabs[0 : n]);
-	} else {
-		for n > len(Blanks) {
-			m, err := b.writer.Write(Blanks);
-			n -= len(Blanks);
+		padding = Tabs;
+	}
+	
+	for n > len(padding) {
+		err = b.Write0(padding);
+		if err != nil {
+			goto exit;
 		}
-		m, err := b.writer.Write(Blanks[0 : n]);
+		n -= len(padding);
 	}
+	err = b.Write0(padding[0 : n]);
+
+exit:
+	return err;
 }
 
 
-func (b *TabWriter) PrintLines(pos int, line0, line1 int) int {
+func (b *TabWriter) WriteLines(pos0 int, line0, line1 int) (pos int, err *os.Error) {
+	pos = pos0;
 	for i := line0; i < line1; i++ {
 		line := b.Line(i);
 		for j := 0; j < line.Len(); j++ {
 			w := line.At(j);
-			m, err := b.writer.Write(b.buf.a[pos : pos + w]);
-			if m != w {
-				panic();
+			err = b.Write0(b.buf.a[pos : pos + w]);
+			if err != nil {
+				goto exit;
 			}
 			pos += w;
 			if j < b.widths.Len() {
-				b.Padding(w, b.widths.At(j));
+				err = b.WritePadding(w, b.widths.At(j));
+				if err != nil {
+					goto exit;
+				}
 			}
 		}
-		m, err := b.writer.Write(Newline);
+		err = b.Write0(Newline);
+		if err != nil {
+			goto exit;
+		}
 	}
-	return pos;
+
+exit:
+	return pos, err;
 }
 
 
-func (b *TabWriter) Format(pos int, line0, line1 int) int {
-	column := b.widths.Len();
-	
+// TODO use utflen for correct formatting
+func utflen(buf *[]byte) int {
+	n := 0;
+	for i := 0; i < len(buf); i++ {
+		if buf[i]&0xC0 != 0x80 {
+			n++
+		}
+	}
+	return n
+}
+
+
+func (b *TabWriter) Format(pos0 int, line0, line1 int) (pos int, err *os.Error) {
+	pos = pos0;
+	column := b.widths.Len();	
 	last := line0;
 	for this := line0; this < line1; this++ {
 		line := b.Line(this);
@@ -206,7 +245,10 @@ func (b *TabWriter) Format(pos int, line0, line1 int) int {
 			// (note that the last cell per line is ignored)
 			
 			// print unprinted lines until beginning of block
-			pos = b.PrintLines(pos, last, this);
+			pos, err = b.WriteLines(pos, last, this);
+			if err != nil {
+				goto exit;
+			}
 			last = this;
 			
 			// column block begin
@@ -214,9 +256,8 @@ func (b *TabWriter) Format(pos int, line0, line1 int) int {
 			for ; this < line1; this++ {
 				line = b.Line(this);
 				if column < line.Len() - 1 {
-					// cell exists in this column
-					// update width
-					w := line.At(column) + 1; // 1 = minimum space between cells
+					// cell exists in this column => update width
+					w := line.At(column) + b.padding;
 					if w > width {
 						width = w;
 					}
@@ -226,85 +267,77 @@ func (b *TabWriter) Format(pos int, line0, line1 int) int {
 			}
 			// column block end
 
-			if b.usetabs {
-				// make width a multiple of the tab width
-				width = ((width + b.tabwidth - 1) / b.tabwidth) * b.tabwidth;
-			}
-			
 			// format and print all columns to the right of this column
 			// (we know the widths of this column and all columns to the left)
 			b.widths.Push(width);
-			pos = b.Format(pos, last, this);
+			pos, err = b.Format(pos, last, this);
 			b.widths.Pop();
 			last = this;
 		}
 	}
 
 	// print unprinted lines until end
-	return b.PrintLines(pos, last, line1);
+	pos, err = b.WriteLines(pos, last, line1);
+	
+exit:
+	return pos, err;
 }
 
 
-func (b *TabWriter) EmptyLine() bool {
-	return b.LastLine().Len() == 0 && b.width == 0;
+func (b *TabWriter) Append(buf *[]byte) {
+	b.buf.Append(buf);
+	b.width += len(buf);
 }
 
 
-func (b *TabWriter) Tab() {
-	b.LastLine().Push(b.width);
+/* export */ func (b *TabWriter) Flush() *os.Error {
+	dummy, err := b.Format(0, 0, b.lines.Len());
+	// reset (even in the presence of errors)
+	b.buf.Clear();
 	b.width = 0;
-}
-
-
-func (b *TabWriter) Newline() {
-	b.Tab();  // add last cell to current line
-
-	if b.LastLine().Len() == 1 {
-		// The current line has only one cell which does not have an impact
-		// on the formatting of the following lines (the last cell per line
-		// is ignored by Format), thus we can print the TabWriter contents.
-		if b.widths.Len() != 0 {
-			panic("internal error");
-		}
-		b.Format(0, 0, b.lines.Len());
-		if b.widths.Len() != 0 {
-			panic("internal error");
-		}
-
-		// reset TabWriter
-		b.width = 0;
-		b.buf.Clear();
-		b.lines.Init(0);
-	}
-
+	b.lines.Init(0);
 	b.AddLine();
+	return err;
 }
 
 
-func (b *TabWriter) Write(buf *[]byte) (i int, err *os.Error) {
+/* export */ func (b *TabWriter) Write(buf *[]byte) (written int, err *os.Error) {
 	i0, n := 0, len(buf);
-	for i = 0; i < n; i++ {
-		switch buf[i] {
-		case '\t':
-			b.width += i - i0;
-			b.buf.Append(buf[i0 : i]);
-			i0 = i + 1;  // don't append '\t'
-			b.Tab();
-		case '\n':
-			b.width += i - i0;
-			b.buf.Append(buf[i0 : i]);
-			i0 = i + 1;  // don't append '\n'
-			b.Newline();
+	
+	// split text into cells
+	for i := 0; i < n; i++ {
+		if ch := buf[i]; ch == '\t' || ch == '\n' {
+			b.Append(buf[i0 : i]);
+			i0 = i + 1;  // exclude ch from (next) cell
+
+			// terminate cell
+			b.LastLine().Push(b.width);
+			b.width = 0;
+
+			if ch == '\n' {
+				if b.LastLine().Len() == 1 {
+					// The last line has only one cell which does not have an
+					// impact on the formatting of the following lines (the
+					// last cell per line is ignored by Format), thus we can
+					// flush the TabWriter contents.
+					err = b.Flush();
+					if err != nil {
+						return i0, err;
+					}
+				} else {
+					// We can't flush yet - just add a new line.
+					b.AddLine();
+				}
+			}
 		}
 	}
-	b.width += n - i0;
-	b.buf.Append(buf[i0 : n]);
-	return i, nil;
+	
+	// append leftover text
+	b.Append(buf[i0 : n]);
+	return n, nil;
 }
 
 
-export func MakeTabWriter(writer io.Write, usetabs bool, tabwidth int) *TabWriter {
-	b := new(TabWriter);
-	b.Init(writer, usetabs, tabwidth);
-	return b;
+export func New(writer io.Write, tabwidth, padding int, usetabs bool) *TabWriter {
+	return new(TabWriter).Init(writer, tabwidth, padding, usetabs)
 }
diff --git a/usr/gri/pretty/untab.go b/usr/gri/pretty/untab.go
index a2232b351..d2a26f438 100644
--- a/usr/gri/pretty/untab.go
+++ b/usr/gri/pretty/untab.go
@@ -14,8 +14,8 @@ import (
 
 
 var (
-	usetabs = flag.Bool("usetabs", false, nil, "align with tabs instead of blanks");
 	tabwidth = flag.Int("tabwidth", 4, nil, "tab width");
+	usetabs = flag.Bool("usetabs", false, nil, "align with tabs instead of blanks");
 )
 
 
@@ -36,7 +36,7 @@ func Untab(name string, src *os.FD, dst *tabwriter.TabWriter) {
 
 func main() {
 	flag.Parse();
-	dst := tabwriter.MakeTabWriter(os.Stdout, usetabs.BVal(), int(tabwidth.IVal()));
+	dst := tabwriter.New(os.Stdout, int(tabwidth.IVal()), 1, usetabs.BVal());
 	if flag.NArg() > 0 {
 		for i := 0; i < flag.NArg(); i++ {
 			name := flag.Arg(i);