rbuffer: Reimplement as a ring buffer and decouple from rstream

Extract the RBuffer class from rstream.c and reimplement it as a ring buffer,
a more efficient version that doesn't need to relocate memory.

The old rbuffer_read/rbuffer_write interfaces are kept for simple
reading/writing, and the RBUFFER_UNTIL_{FULL,EMPTY} macros are introduced to
hide wrapping logic when more control is required(such as passing the buffer
pointer to a library function that writes directly to the pointer)

Also add a basic infrastructure for writing helper C files that are only
compiled in the unit test library, and use this to write unit tests for RBuffer
which contains some macros that can't be accessed directly by luajit.

Helped-by: oni-link <knil.ino@gmail.com>
Reviewed-by: oni-link <knil.ino@gmail.com>
Reviewed-by: Scott Prager <splinterofchaos@gmail.com>
Reviewed-by: Justin M. Keyes <justinkz@gmail.com>
Reviewed-by: Michael Reed <m.reed@mykolab.com>

1 files changed, 350 insertions, 0 deletions

diff --git a/test/unit/rbuffer_spec.lua b/test/unit/rbuffer_spec.lua
new file mode 100644
index 0000000000..89136410d3
--- /dev/null
+++ b/test/unit/rbuffer_spec.lua
@@ -0,0 +1,350 @@
+local helpers = require("test.unit.helpers")
+
+local ffi     = helpers.ffi
+local eq      = helpers.eq
+local cstr    = helpers.cstr
+local to_cstr = helpers.to_cstr
+
+local rbuffer = helpers.cimport("./test/unit/fixtures/rbuffer.h")
+
+describe('rbuffer functions', function()
+  local capacity = 16
+  local rbuf
+
+  local function inspect()
+    return ffi.string(rbuf.start_ptr, capacity)
+  end
+
+  local function write(str)
+    local buf = to_cstr(str)
+    return rbuffer.rbuffer_write(rbuf, buf, #str)
+  end
+
+  local function read(len)
+    local buf = cstr(len)
+    len = rbuffer.rbuffer_read(rbuf, buf, len)
+    return ffi.string(buf, len)
+  end
+
+  local function get(idx)
+    return ffi.string(rbuffer.rbuffer_get(rbuf, idx), 1)
+  end
+
+  before_each(function()
+    rbuf = ffi.gc(rbuffer.rbuffer_new(capacity), rbuffer.rbuffer_free)
+    -- fill the internal buffer with the character '0' to simplify inspecting
+    ffi.C.memset(rbuf.start_ptr, string.byte('0'), capacity)
+  end)
+
+  describe('RBUFFER_UNTIL_FULL', function()
+    local chunks
+
+    local function collect_write_chunks()
+      rbuffer.ut_rbuffer_each_write_chunk(rbuf, function(wptr, wcnt)
+        table.insert(chunks, ffi.string(wptr, wcnt))
+      end)
+    end
+
+    before_each(function()
+      chunks = {}
+    end)
+
+    describe('with empty buffer in one contiguous chunk', function()
+      it('is called once with the empty chunk', function()
+        collect_write_chunks()
+        eq({'0000000000000000'}, chunks)
+      end)
+    end)
+
+    describe('with partially empty buffer in one contiguous chunk', function()
+      before_each(function()
+        write('string')
+      end)
+
+      it('is called once with the empty chunk', function()
+        collect_write_chunks()
+        eq({'0000000000'}, chunks)
+      end)
+    end)
+
+    describe('with filled buffer in one contiguous chunk', function()
+      before_each(function()
+        write('abcdefghijklmnopq')
+      end)
+
+      it('is not called', function()
+        collect_write_chunks()
+        eq({}, chunks)
+      end)
+    end)
+
+    describe('with buffer partially empty in two contiguous chunks', function()
+      before_each(function()
+        write('1234567890')
+        read(8)
+      end)
+
+      it('is called twice with each filled chunk', function()
+        collect_write_chunks()
+        eq({'000000', '12345678'}, chunks)
+      end)
+    end)
+
+    describe('with buffer empty in two contiguous chunks', function()
+      before_each(function()
+        write('12345678')
+        read(8)
+      end)
+
+      it('is called twice with each filled chunk', function()
+        collect_write_chunks()
+        eq({'00000000', '12345678'}, chunks)
+      end)
+    end)
+
+    describe('with buffer filled in two contiguous chunks', function()
+      before_each(function()
+        write('12345678')
+        read(8)
+        write('abcdefghijklmnopq')
+      end)
+
+      it('is not called', function()
+        collect_write_chunks()
+        eq({}, chunks)
+      end)
+    end)
+  end)
+
+  describe('RBUFFER_UNTIL_EMPTY', function()
+    local chunks
+
+    local function collect_read_chunks()
+      rbuffer.ut_rbuffer_each_read_chunk(rbuf, function(rptr, rcnt)
+        table.insert(chunks, ffi.string(rptr, rcnt))
+      end)
+    end
+
+    before_each(function()
+      chunks = {}
+    end)
+
+    describe('with empty buffer', function()
+      it('is not called', function()
+        collect_read_chunks()
+        eq({}, chunks)
+      end)
+    end)
+
+    describe('with partially filled buffer in one contiguous chunk', function()
+      before_each(function()
+        write('string')
+      end)
+
+      it('is called once with the filled chunk', function()
+        collect_read_chunks()
+        eq({'string'}, chunks)
+      end)
+    end)
+
+    describe('with filled buffer in one contiguous chunk', function()
+      before_each(function()
+        write('abcdefghijklmnopq')
+      end)
+
+      it('is called once with the filled chunk', function()
+        collect_read_chunks()
+        eq({'abcdefghijklmnop'}, chunks)
+      end)
+    end)
+
+    describe('with buffer partially filled in two contiguous chunks', function()
+      before_each(function()
+        write('1234567890')
+        read(10)
+        write('long string')
+      end)
+
+      it('is called twice with each filled chunk', function()
+        collect_read_chunks()
+        eq({'long s', 'tring'}, chunks)
+      end)
+    end)
+
+    describe('with buffer filled in two contiguous chunks', function()
+      before_each(function()
+        write('12345678')
+        read(8)
+        write('abcdefghijklmnopq')
+      end)
+
+      it('is called twice with each filled chunk', function()
+        collect_read_chunks()
+        eq({'abcdefgh', 'ijklmnop'}, chunks)
+      end)
+    end)
+  end)
+
+  describe('RBUFFER_EACH', function()
+    local chars
+
+    local function collect_chars()
+      rbuffer.ut_rbuffer_each(rbuf, function(c, i)
+        table.insert(chars, {string.char(c), tonumber(i)})
+      end)
+    end
+    before_each(function()
+      chars = {}
+    end)
+
+    describe('with empty buffer', function()
+      it('is not called', function()
+        collect_chars()
+        eq({}, chars)
+      end)
+    end)
+
+    describe('with buffer filled in two contiguous chunks', function()
+      before_each(function()
+        write('1234567890')
+        read(10)
+        write('long string')
+      end)
+
+      it('collects each character and index', function()
+        collect_chars()
+        eq({{'l', 0}, {'o', 1}, {'n', 2}, {'g', 3}, {' ', 4}, {'s', 5},
+            {'t', 6}, {'r', 7}, {'i', 8}, {'n', 9}, {'g', 10}}, chars)
+      end)
+    end)
+  end)
+
+  describe('RBUFFER_EACH_REVERSE', function()
+    local chars
+
+    local function collect_chars()
+      rbuffer.ut_rbuffer_each_reverse(rbuf, function(c, i)
+        table.insert(chars, {string.char(c), tonumber(i)})
+      end)
+    end
+    before_each(function()
+      chars = {}
+    end)
+
+    describe('with empty buffer', function()
+      it('is not called', function()
+        collect_chars()
+        eq({}, chars)
+      end)
+    end)
+
+    describe('with buffer filled in two contiguous chunks', function()
+      before_each(function()
+        write('1234567890')
+        read(10)
+        write('long string')
+      end)
+
+      it('collects each character and index', function()
+        collect_chars()
+        eq({{'g', 10}, {'n', 9}, {'i', 8}, {'r', 7}, {'t', 6}, {'s', 5},
+            {' ', 4}, {'g', 3}, {'n', 2}, {'o', 1}, {'l', 0}}, chars)
+      end)
+    end)
+  end)
+
+  describe('rbuffer_cmp', function()
+    local function cmp(str)
+      local rv = rbuffer.rbuffer_cmp(rbuf, to_cstr(str), #str)
+      if rv == 0 then
+        return 0
+      else
+        return rv / math.abs(rv)
+      end
+    end
+
+    describe('with buffer filled in two contiguous chunks', function()
+      before_each(function()
+        write('1234567890')
+        read(10)
+        write('long string')
+      end)
+
+      it('compares the common longest sequence', function()
+        eq(0, cmp('long string'))
+        eq(0, cmp('long strin'))
+        eq(-1, cmp('long striM'))
+        eq(1, cmp('long strio'))
+        eq(0, cmp('long'))
+        eq(-1, cmp('lonG'))
+        eq(1, cmp('lonh'))
+      end)
+    end)
+
+    describe('with empty buffer', function()
+      it('returns 0 since no characters are compared', function()
+        eq(0, cmp(''))
+      end)
+    end)
+  end)
+
+  describe('rbuffer_write', function()
+    it('fills the internal buffer and returns the write count', function()
+      eq(12, write('short string'))
+      eq('short string0000', inspect())
+    end)
+
+    it('wont write beyond capacity', function()
+      eq(16, write('very very long string'))
+      eq('very very long s', inspect())
+    end)
+  end)
+
+  describe('rbuffer_read', function()
+    it('reads what was previously written', function()
+      write('to read')
+      eq('to read', read(20))
+    end)
+
+    it('reads nothing if the buffer is empty', function()
+      eq('', read(20))
+      write('empty')
+      eq('empty', read(20))
+      eq('', read(20))
+    end)
+  end)
+
+  describe('rbuffer_get', function()
+    it('fetch the pointer at offset, wrapping if required', function()
+      write('1234567890')
+      read(10)
+      write('long string')
+      eq('l', get(0))
+      eq('o', get(1))
+      eq('n', get(2))
+      eq('g', get(3))
+      eq(' ', get(4))
+      eq('s', get(5))
+      eq('t', get(6))
+      eq('r', get(7))
+      eq('i', get(8))
+      eq('n', get(9))
+      eq('g', get(10))
+    end)
+  end)
+
+  describe('wrapping behavior', function()
+    it('writing/reading wraps across the end of the internal buffer', function()
+      write('1234567890')
+      eq('1234', read(4))
+      eq('5678', read(4))
+      write('987654321')
+      eq('3214567890987654', inspect())
+      eq('90987654321', read(20))
+      eq('', read(4))
+      write('abcdefghijklmnopqrs')
+      eq('nopabcdefghijklm', inspect())
+      eq('abcdefghijklmnop', read(20))
+    end)
+  end)
+end)