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This is one of several changes that were part of a larger rewrite
which I made in early 2019 after switching to the new number literal
syntax implementation. The purpose of the rewrite was to simplify
reading of source code (Unicode character by character) and speed up
the scanner but was never submitted for review due to other priorities.
Part 3 of 3:
This change contains a complete rewrite of source.go, the file that
implements reading individual Unicode characters from the source.
The new implementation is easier to use and has simpler literal
buffer management, resulting in faster scanner and thus parser
performance.
Thew new source.go (internal) API is centered around nextch() which
advances the scanner by one character. The scanner has been adjusted
around nextch() and now consistently does one character look-ahead
(there's no need for complicated ungetr-ing anymore). Only in one
case backtrack is needed (when finding '..' rather than '...') and
that case is now more cleanly solved with the new reset() function.
Measuring line/s parsing peformance by running
go test -run StdLib -fast -skip "syntax/(scanner|source)\.go"
(best of 5 runs on "quiet" MacBook Pro, 3.3GHz Dual-Core i7, 16GB RAM,
OS X 10.15.3) before and after shows consistently 3-5% improvement of
line parsing speed:
old: parsed 1788155 lines (3969 files) in 1.255520307s (1424234 lines/s)
new: parsed 1788155 lines (3969 files) in 1.213197037s (1473919 lines/s)
(scanner.go and parser.go are skipped because this CL changed those files.)
Change-Id: Ida947f4b538d42eb2d2349062c69edb6c9e5ca66
Reviewed-on: https://go-review.googlesource.com/c/go/+/221603
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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Make it possible to "unread" more than one byte before the most
recently read rune. Use a better name than ungetr2 and make it
slightly more efficient.
R=Go1.13
Change-Id: I45d5dfa11e508259a972ca6560d1f78d7a51fe15
Reviewed-on: https://go-review.googlesource.com/c/158957
Reviewed-by: Russ Cox <rsc@golang.org>
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The source.offs field was intended for computing line offsets which
may allow a tiny optimization (see TODO in source.go). We haven't
done the optimization, so for now just remove the field to avoid
confusion. It's trivially added if needed.
While at it, also:
- Fix comment for ungetr2.
- Make sure sentinel is present even if reading from the io.Reader failed.
Change-Id: Ib056c6478030b3fe5fec29045362c8161ff3d19e
Reviewed-on: https://go-review.googlesource.com/c/152763
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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R=go1.11
In order to collect comments in the AST and for error testing purposes,
the scanner needs to not only recognize and skip comments, but also be
able to report them if so desired. This change adds a mode flag to the
scanner's init function which controls the scanner behavior around
comments.
In the common case where comments are not needed, there must be no
significant overhead. Thus, comments are reported via a handler upcall
rather than being returned as a _Comment token (which the parser would
have to filter out with every scanner.next() call).
Because the handlers for error messages, directives, and comments all
look the same (they take a position and text), and because directives
look like comments, and errors never start with a '/', this change
simplifies the scanner's init call to only take one (error) handler
instead of 2 or 3 different handlers with identical signature. It is
trivial in the handler to determine if we have an error, directive,
or general comment.
Finally, because directives are comments, when reporting directives
the full comment text is returned now rather than just the directive
text. This simplifies the implementation and makes the scanner API
more regular. Furthermore, it provides important information about
the comment style used by a directive, which may matter eventually
when we fully implement /*line file:line:col*/ directives.
Change-Id: I2adbfcebecd615e4237ed3a832b6ceb9518bf09c
Reviewed-on: https://go-review.googlesource.com/88215
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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The previous code seems to have an off-by-1 in it somewhere, the
consequence being that we didn't properly preserve all of the old
buffer contents that we intended to.
After spending a while looking at the existing window-shifting logic,
I wasn't able to understand exactly how it was supposed to work or
where the issue was, so I rewrote it to be (at least IMO) more
obviously correct.
Fixes #21938.
Change-Id: I1ed7bbc1e1751a52ab5f7cf0411ae289586dc345
Reviewed-on: https://go-review.googlesource.com/64830
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
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We could leave it alone and fix line offset (column) numbers when
reporting errors, but that is likely to cause confusion (internal
numbers don't match reported numbers). Instead, switch to default
numbering starting at 1.
For package syntax-internal use only, introduced constants defining
the line and column bases, and use them throughout the code and its
tests. It is possible to change these constants and package syntax
will continue to work. But changing them is going to break any client
that makes explicit assumptions about line and column numbers (which
is "all of them").
Change-Id: Ia3d136a8ec8d9372ed9c05ca47d3dff222cf030e
Reviewed-on: https://go-review.googlesource.com/37996
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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rune count for column value
This will only become user-visible if error messages show column information.
Per the discussion in #10324.
For #10324.
Change-Id: I5959c1655aba74bb1a22fdc261cd728ffcfa6912
Reviewed-on: https://go-review.googlesource.com/34244
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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positions
- use syntax.Pos in syntax.Error (rather than line, col)
- use syntax.Pos in syntax.PragmaHandler (rather than just line)
- update uses
- better documentation in various places
Also:
- make Pos methods use Pos receiver (rather than *Pos)
Reviewed in and cherry-picked from https://go-review.googlesource.com/#/c/33891/.
With minor adjustments to noder.go to make merge compile.
Change-Id: I5507cea6c2be46a7677087c1aeb69382d31033eb
Reviewed-on: https://go-review.googlesource.com/34236
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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Reviewed in and cherry-picked from https://go-review.googlesource.com/#/c/33873/.
- simplify error handling in source.go
(move handling of first error into parser, where it belongs)
- clean up error handling in scanner.go
- move pragma and position base handling from scanner
to parser where it belongs
- have separate error methods in parser to avoid confusion
with handlers from scanner.go and source.go
- (source.go) and (scanner.go, source.go, tokens.go)
may be stand-alone packages if so desired, which means
these files are now less entangled and easier to maintain
Change-Id: I81510fc7ef943b78eaa49092c0eab2075a05878c
Reviewed-on: https://go-review.googlesource.com/34235
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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for nodes
Reviewed in and cherry-picked from https://go-review.googlesource.com/#/c/33758/.
Minor adjustments in noder.go to fix merge.
Change-Id: Ibe429e327c7f8554f8ac205c61ce3738013aed98
Reviewed-on: https://go-review.googlesource.com/34231
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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- define syntax.Error for cleaner error reporting
- abort parsing after first error if no error handler is installed
- make sure to always report the first error, if any
- document behavior of API calls
- while at it: rename ReadXXX -> ParseXXX (clearer)
- adjust cmd/compile noder.go accordingly
Fixes #17774.
Change-Id: I7893eedea454a64acd753e32f7a8bf811ddbb03c
Reviewed-on: https://go-review.googlesource.com/32950
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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Syntax tree nodes, scanner, parser, basic printers.
Builds syntax trees for entire Go std lib at a rate of ~1.8M lines/s
in warmed up state (MacMini, 2.3 GHz Intel Core i7, 8GB RAM):
$ go test -run StdLib -fast
parsed 1074617 lines (2832 files) in 579.66364ms (1853863 lines/s)
allocated 282.212Mb (486.854Mb/s)
PASS
Change-Id: Ie26d9a7bf4e5ff07457aedfcc9b89f0eba72ae3f
Reviewed-on: https://go-review.googlesource.com/27195
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
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