Improve hash module

Update sha1 ctx every 64KB instead of consuming memory until the final
step.

Add a hash_file() function which takes a path and hashes its content.

Signed-off-by: Tobias Ulmer <tu@emlix.com>

diff --git a/generic/hash.lua b/generic/hash.lua
index 99d67435d59577a573711ce7ff13caf60ece8706..95e8f15d9021ce3ea539a244a4aa1d261006b794 100644 (file)
--- a/generic/hash.lua
+++ b/generic/hash.lua
@@ -33,10 +33,15 @@ require("sha1")
 -- @return nil, an error string on error
 function hash_start()
        local hc = {}
+
        for k,v in pairs(hash) do
                hc[k] = v
        end
+
+       hc.ctx = sha1.sha1_init()
        hc.data = ""
+       hc.datalen = 0
+
        return hc
 end
 
@@ -44,21 +49,72 @@ end
 -- @param hc the hash context
 -- @param data string: data
 function hash_append(hc, data)
-       -- append the data
+       assert(type(hc) == "table" and type(hc.ctx) == "userdata")
+       assert(type(data) == "string")
+
        hc.data = hc.data .. data
+       hc.datalen = hc.datalen + string.len(data)
+
+       -- Consume data and update hash whenever 64KB are available
+       if hc.datalen >= 64*1024 then
+               hc.ctx:update(hc.data)
+               hc.data = ""
+               hc.datalen = 0
+       end
 end
 
+--- hash a line
+-- @param hc the hash context
+-- @param data string: data to hash, a newline is appended
 function hash_line(hc, data)
        hash_append(hc, data .. "\n")
 end
 
+--- hash a file
+-- @param hc the hash context
+-- @param path string: the full path to the file
+-- @return true on success, nil on error
+-- @return nil, error object on failure
+function hash_file(hc, path)
+       assert(type(hc) == "table" and type(hc.ctx) == "userdata")
+       assert(type(path) == "string")
+
+       local fd = io.open(path, "r")
+       if not fd then
+               return nil, new_error("could not open file '%s'", path)
+       end
+
+       local buf = ""
+       while true do
+               buf = fd:read(64*1024)
+               if buf == nil then
+                       break
+               end
+
+               hash_append(hc, buf)
+       end
+
+       fd:close()
+
+       return true
+end
+
 --- add hash data
 -- @param hc the hash context
 -- @return the hash value, or nil on error
 -- @return an error string on error
 function hash_finish(hc)
-       local ctx = sha1.sha1_init()
-       ctx:update(hc.data)
-       hc.sha1 = string.lower(ctx:final())
-       return hc.sha1
+       assert(type(hc) == "table" and type(hc.ctx) == "userdata")
+
+       hc.ctx:update(hc.data)
+
+       local cs = string.lower(hc.ctx:final())
+       assert(string.len(cs) == 40)
+
+       -- Destroy the hash context to catch errors
+       for k,_ in pairs(hc) do
+               hc[k] = nil
+       end
+
+       return cs
 end