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gj

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CLI and Vim plugin to search codes instantly

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# gj #

Usually we have two needs when reading codes:

* Find out the definition (or declaration) of `foo`. `foo` may be a class, method or a function.
* Find out all places which use `foo`.

`grep -R foo .` is good for the second case since it won't miss any direct use. However, `grep` is not
fast enough for large projects and it's somewhat inconvent for the first case. This is why [gj] is created.

The goals of [gj] from high to low are:

* Low miss: it's bad to miss a caller when you refactor codes or want to find out who modifies the target variable.
* Speed: list possible targets instantly.
* Less reading time: interactively narrow down to your target.

[gj] is used in two ways:

* Run as an interactive command line tool to edit and filter candidate files interactively.
* As a plugin in [Vim] to find files which contain the word under the cursor.

## Demo ##

![Example usage of gj](https://raw.github.com/fcamel/screenshots/master/gj/gj_demo.gif)

1. `gj -i`: build the index.
2. `gj main argc argv`: find out the main functions. C/C++ main() typically has these three keywords.
3. `example`: keep files with the substring *example* in the file name.
4. `!test`: remove files with the substring *test* in the file name.
5. `1`: Use [Vim] to edit the first file and jump to the corresponding line.
6. Exit [Vim] and back to [gj].
7. `2`: Edit the second one.
8. In [Vim], `<leader>G` under *DoLogin*: list possible definitions or declarations of *DoLogin*.
9. In [Vim], `<leader>g` under *DoLogin*: list all callers, definitions or declarations of *DoLogin*.

## Installation ##

### Prerequisite ###

[gj] is based on [ID Utils] which finds patterns instantly. Install [ID Utils] by:

```bash
$ sudo apt-get install id-utils  # Debian / Ubuntu
$ sudo port install idutils      # OS X with MacPorts
$ brew install idutils           # OS X with Homebrew
```

### Vim Plugin + Command Line Tool ###

#### Vundle ####

Install [gj.vim] via [Vundle]. Please refer documents in [Vundle]: a highly recommended tool to manage [Vim] plugins.

#### Vim plugins ####

Add these to your `.vimrc`:

```vim
Plugin 'fcamel/gj'
```

Then launch `vim` and run `:VundleInstall`.

In order to use the command line tool, add this to your `$HOME/.bashrc` (or other shell config file):

```bash
export PATH="$PATH:$HOME/.vim/bundle/gj/bin"
```

### (optional) Command Line Tool Only ###

```bash
$ cd /path/to/somewhere/
$ git clone https://github.com/fcamel/gj
$ export PATH="$PATH:`pwd`/bin"
```

## Usage ##

### Command Line Tool ###

```bash
$ cd /path/to/project/
$ gj -i                 # Build the index.
$ gj PATTERN            # Find out PATTERN
$ gj -p BASE PATTERN    # Find out PATTERN which under BASE folder
```

Then follow the instructions in terminal.

If you don't use [Vim] as your main editor, please set the environment variable `EDITOR` to your favorite editor.
However, currently only [Vim] supports "jump to the line" and "highlight the searched pattern" when opening
the file.

Other useful arguments:

```bash
$ gj -s LITERAL         # Show all symbols which contain LITERAL (case-insensitive)
$ gj -sv LITERAL        # Same as above, but also display file lists for each symbol.
$ gj -d PATTERN         # Try to find out PATTERN's definition or declaration. Work for C++ or Python. 
```

Examples of using [gj] for special scenarios:

```bash
$ gj TYPE typedef       # Find the declaration of typedef TYPE.
$ gj CLASS public       # Find all classes which inherit from CLASS
$ gj CLASS METHOD       # Find definition of a C++ method.
$ gj FILE include       # Find all files which include FILE.
                        # You can enter "1-N" to select all files. This is useful to
                        # refactor include paths after moving a header to a different path.
```
* forget method name: gj -s SUBSTRING
* need to filter by file name: gj -s -v SUBSTRING
* find assignment via "=": gj SYMBOL =

#### Advanced Feature ####

[gj] supports two kinds of indexes. 
* text index: Index the source codes via [ID Utils].
* binary index: Index the debug info of the ELF binaries ([DWARF]) via `readelf` and `nm`.

To use the binary index, you need to build the binaries with the debug info (e.g., `g++ -g`) and tell [gj] the path of binaries:

```bash
$ gj -c                  # Generate the config file ".gjconfig"
( edit .giconfig and fill the paths of binaries. )

$ gj -i                  # Now gj index both the source codes and the binaries.
```

Then use `gj -D SYMBOL` to search the definitions. The result is much faster and more accurately. For example, to find `main`, we need the keywords "argc" and "argv" to filter the candidates previously. Now just `gj -D main` is enough.

**NOTE** I only test this feature on Linux and haven't tested it on other platforms.

### Vim Plugin ###

In Normal mode:

* `<leader>g`: Find all matched files of the word under the cursor.
* `<leader>G`: Find all possible declarations or definitions of the word under the cursor.
* `<leader>d`: Find all possible definitions of the word under the cursor based on the index of [DWARF].

Then use the following commands in quickfix window:

* `o` : open file (same as enter).
* `go`: open file (but maintain focus in quickfix window). 
* `t` : open in a new tab.
* `T` : open in new tab silently.
* `h` : open in horizontal split.
* `H` : open in horizontal split silently.
* `v` : open in vertical split.
* `gv`: open in vertical split silently.
* `q` : close the quickfix window.

## Troubleshooting ##

### How to index the shared library on Ubuntu? ###

Take libgdbm as an example. Here is how:
```
$ apt-get source libgdbm3:amd64  # Get the source codes.
$ cd gdbm-1.8.3/
$ ./configure && make
$ make --dry-run install | grep libtool  # Find out how to build the shared library.
/bin/bash ./libtool --mode=install /usr/bin/install -c -T libgdbm.la /usr/local/lib/libgdbm.la
$ mkdir local
$ /bin/bash ./libtool --mode=install /usr/bin/install -c -T libgdbm.la `pwd`/local/libgdbm.la  # Create libgdbm.so in local/.
(...)
$ /bin/bash ./libtool --mode=install /usr/bin/install -c -T libgdbm_compat.la `pwd`/local/libgdbm_compat.la
(...)
$ gj_index.py local/*.so
Index local/libgdbm_compat.so ...
Index local/libgdbm.so ...
Save the index to gj.index
$ gj -D gdbm_close -b
./gdbmclose.c:42:0:gdbm_close
$ gj -D dbm_delete -b
./dbmdelete.c:45:0:dbm_delete
```

### How to use gj on Fedora? ###

[Fedora doesn't support id-utils](https://lists.fedoraproject.org/pipermail/devel/2012-May/166914.html). You need to build it by yourself and copy the required binary to your `PATH`.

**Step 1**: Fetch the code and generate build files.
```
$ wget https://ftp.gnu.org/gnu/idutils/idutils-4.6.tar.xz
$ tar xf idutils-4.6.tar.xz
$ cd idutils-4.6/
$ ./configure
$ make
```
**Step 2**: Patch `lib/stdio.h` to make the build pass:

Comment out all `_GL_WARN_ON_USE (gets, "gets is a security hole - use fgets instead");` in `lib/stdio.h`. The file is generated by `make` and `id-utils` doesn't use `gets()` anywhere.

**Step 3**: Continue the build and copy `mkid` and `gid` to some directory in your `PATH`.
```
$ make
$ mkdir -p ~/bin
$ cp src/mkid src/gid ~/bin/
```

## Todo ##

* Improve `-d`'s speed.
* Improve `-d`'s accuracy.
* Support Emacs as well.
* Add more screenshots.

[gj]:https://github.com/fcamel/gj
[gj.vim]:https://github.com/fcamel/gj/blob/master/plugin/gj.vim
[Vim]:http://www.vim.org/
[ID Utils]:http://www.gnu.org/software/idutils/
[Vundle]:http://github.com/gmarik/vundle
[DWARF]:https://en.wikipedia.org/wiki/DWARF

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