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tabwriter: use panic/recover to handle errors

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R=rsc, r
CC=golang-dev
https://golang.org/cl/864042
This commit is contained in:
Robert Griesemer 2010-03-31 16:01:22 -07:00
parent 7de610cc61
commit f67c90f941
1 changed files with 47 additions and 50 deletions
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97
src/pkg/tabwriter/tabwriter.go
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@ -221,23 +221,30 @@ func (b *Writer) dump() {
}
func (b *Writer) write0(buf []byte) os.Error {
// local error wrapper so we can distinguish os.Errors we want to return
// as errors from genuine panics (which we don't want to return as errors)
type osError struct {
err os.Error
}
func (b *Writer) write0(buf []byte) {
n, err := b.output.Write(buf)
if n != len(buf) && err == nil {
err = os.EIO
}
return err
if err != nil {
panic(osError{err})
}
}
func (b *Writer) writeN(src []byte, n int) os.Error {
func (b *Writer) writeN(src []byte, n int) {
for n > len(src) {
if err := b.write0(src); err != nil {
return err
}
b.write0(src)
n -= len(src)
}
return b.write0(src[0:n])
b.write0(src[0:n])
}
@ -247,11 +254,11 @@ var (
)
func (b *Writer) writePadding(textw, cellw int, useTabs bool) os.Error {
func (b *Writer) writePadding(textw, cellw int, useTabs bool) {
if b.padbytes[0] == '\t' || useTabs {
// padding is done with tabs
if b.tabwidth == 0 {
return nil // tabs have no width - can't do any padding
return // tabs have no width - can't do any padding
}
// make cellw the smallest multiple of b.tabwidth
cellw = (cellw + b.tabwidth - 1) / b.tabwidth * b.tabwidth
@ -259,17 +266,18 @@ func (b *Writer) writePadding(textw, cellw int, useTabs bool) os.Error {
if n < 0 {
panic("internal error")
}
return b.writeN(tabs, (n+b.tabwidth-1)/b.tabwidth)
b.writeN(tabs, (n+b.tabwidth-1)/b.tabwidth)
return
}
// padding is done with non-tab characters
return b.writeN(&b.padbytes, cellw-textw)
b.writeN(&b.padbytes, cellw-textw)
}
var vbar = []byte{'|'}
func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int, err os.Error) {
func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int) {
pos = pos0
for i := line0; i < line1; i++ {
line := b.line(i)
@ -282,40 +290,28 @@ func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int, err os.Error)
if j > 0 && b.flags&Debug != 0 {
// indicate column break
if err = b.write0(vbar); err != nil {
return
}
b.write0(vbar)
}
if c.size == 0 {
// empty cell
if j < b.widths.Len() {
if err = b.writePadding(c.width, b.widths.At(j), useTabs); err != nil {
return
}
b.writePadding(c.width, b.widths.At(j), useTabs)
}
} else {
// non-empty cell
useTabs = false
if b.flags&AlignRight == 0 { // align left
if err = b.write0(b.buf.Bytes()[pos : pos+c.size]); err != nil {
return
}
b.write0(b.buf.Bytes()[pos : pos+c.size])
pos += c.size
if j < b.widths.Len() {
if err = b.writePadding(c.width, b.widths.At(j), false); err != nil {
return
}
b.writePadding(c.width, b.widths.At(j), false)
}
} else { // align right
if j < b.widths.Len() {
if err = b.writePadding(c.width, b.widths.At(j), false); err != nil {
return
}
}
if err = b.write0(b.buf.Bytes()[pos : pos+c.size]); err != nil {
return
b.writePadding(c.width, b.widths.At(j), false)
}
b.write0(b.buf.Bytes()[pos : pos+c.size])
pos += c.size
}
}
@ -324,15 +320,11 @@ func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int, err os.Error)
if i+1 == b.lines.Len() {
// last buffered line - we don't have a newline, so just write
// any outstanding buffered data
if err = b.write0(b.buf.Bytes()[pos : pos+b.cell.size]); err != nil {
return
}
b.write0(b.buf.Bytes()[pos : pos+b.cell.size])
pos += b.cell.size
} else {
// not the last line - write newline
if err = b.write0(newline); err != nil {
return
}
b.write0(newline)
}
}
return
@ -344,7 +336,7 @@ func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int, err os.Error)
// Returns the buffer position corresponding to the beginning of
// line1 and an error, if any.
//
func (b *Writer) format(pos0 int, line0, line1 int) (pos int, err os.Error) {
func (b *Writer) format(pos0 int, line0, line1 int) (pos int) {
pos = pos0
column := b.widths.Len()
for this := line0; this < line1; this++ {
@ -359,9 +351,7 @@ func (b *Writer) format(pos0 int, line0, line1 int) (pos int, err os.Error) {
// to a column)
// print unprinted lines until beginning of block
if pos, err = b.writeLines(pos, line0, this); err != nil {
return
}
pos = b.writeLines(pos, line0, this)
line0 = this
// column block begin
@ -394,7 +384,7 @@ func (b *Writer) format(pos0 int, line0, line1 int) (pos int, err os.Error) {
// 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, err = b.format(pos, line0, this)
pos = b.format(pos, line0, this)
b.widths.Pop()
line0 = this
}
@ -472,12 +462,22 @@ func (b *Writer) terminateCell(htab bool) int {
}
func handlePanic(err *os.Error) {
if e := recover(); e != nil {
*err = e.(osError).err // re-panics if it's not a local osError
}
}
// Flush should be called after the last call to Write to ensure
// that any data buffered in the Writer is written to output. Any
// incomplete escape sequence at the end is simply considered
// complete for formatting purposes.
//
func (b *Writer) Flush() os.Error {
func (b *Writer) Flush() (err os.Error) {
defer b.reset() // even in the presence of errors
defer handlePanic(&err)
// add current cell if not empty
if b.cell.size > 0 {
if b.endChar != 0 {
@ -488,12 +488,9 @@ func (b *Writer) Flush() os.Error {
}
// format contents of buffer
_, err := b.format(0, 0, b.lines.Len())
b.format(0, 0, b.lines.Len())
// reset, even in the presence of errors
b.reset()
return err
return
}
@ -504,6 +501,8 @@ var hbar = []byte("---\n")
// while writing to the underlying output stream.
//
func (b *Writer) Write(buf []byte) (n int, err os.Error) {
defer handlePanic(&err)
// split text into cells
n = 0
for i, ch := range buf {
@ -530,9 +529,7 @@ func (b *Writer) Write(buf []byte) (n int, err os.Error) {
}
if ch == '\f' && b.flags&Debug != 0 {
// indicate section break
if err = b.write0(hbar); err != nil {
return
}
b.write0(hbar)
}
}
}