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@feix feix/read_mysqld_myd.lua
Last active Aug 17, 2018

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-- https://dev.mysql.com/doc/internals/en/layout-record-storage-frame.html
local read_len = function(content, first, l)
local sum = 0
local last = first + l - 1
for i = first, last do
sum = sum * 256 + content[i]
end
return sum
end
local min = function(a, b)
return a <= b and a or b
end
local pad = function(data_len)
local t_len = data_len % 4
if t_len == 0 then
return data_len
else
return data_len - t_len + 4
end
end
local dispatch_record
local read_record = function(content, idx, header_len, data_pos, data_l, next_pos, unused_l)
-- block
-- header
-- data with pad
local rec_type = content[idx]
local data_len = read_len(content, idx+data_pos, data_l)
local unused_len = unused_l > 0 and content[idx+unused_l] or 0
local block_len = pad(header_len + data_len + unused_len)
local next_rec = next_pos > 0 and dispatch_record(content, read_len(content, idx+next_pos, 8)+1) or nil
return {
rec_type=rec_type,
block_len=block_len,
data_len=data_len,
next_rec=next_rec,
data_begin=idx + header_len
}
end
dispatch_record = function(content, idx)
local record = {}
local rec_type = content[idx]
if rec_type == 0 then
record = read_record(content, idx, 20, 1, 3, -1, 0)
elseif rec_type == 1 then
record = read_record(content, idx, 3, 1, 2, -1, 0)
elseif rec_type == 2 then
record = read_record(content, idx, 4, 1, 3, -1, 0)
elseif rec_type == 3 then
record = read_record(content, idx, 4, 1, 2, -1, 3)
elseif rec_type == 4 then
record = read_record(content, idx, 5, 1, 3, -1, 4)
elseif rec_type == 5 then
record = read_record(content, idx, 13, 3, 2, 5, 0)
elseif rec_type == 6 then
record = read_record(content, idx, 15, 4, 3, 7, 0)
elseif rec_type == 7 then
record = read_record(content, idx, 3, 1, 2, -1, 0)
elseif rec_type == 8 then
record = read_record(content, idx, 4, 1, 3, -1, 0)
elseif rec_type == 9 then
record = read_record(content, idx, 4, 1, 2, -1, 3)
elseif rec_type == 10 then
record = read_record(content, idx, 5, 1, 3, -1, 4)
elseif rec_type == 11 then
record = read_record(content, idx, 11, 1, 2, 3, 0)
elseif rec_type == 12 then
record = read_record(content, idx, 12, 1, 3, 4, 0)
elseif rec_type == 13 then
record = read_record(content, idx, 16, 5, 3, 9, 0)
end
return record
end
local read_str = function(content, first, l)
local str = {}
local last = first + l - 1
for i = first, last do
table.insert(str, string.char(content[i]))
end
return table.concat(str)
end
local parse_record = function(content, rec)
local first = rec.data_begin + 3
local host_l = content[first]
local host = read_str(content, first+1, host_l)
local user_l = content[first+host_l+1]
local user = read_str(content, first+host_l+1+1, user_l)
local native = false
local pass_l = 40
local pass = ''
local idx = first + host_l + 1 + 1 + user_l
while true do
local n_pass_l = string.len(pass)
local last = rec.data_begin + rec.data_len
if n_pass_l == 0 then
while idx < last do
if content[idx] == 21 then
native = true
elseif content[idx] == 42 then
idx = idx + 1
break
end
idx = idx + 1
end
end
local n_pass = read_str(content, idx, min(last-idx, pass_l-n_pass_l))
pass = pass .. n_pass
if rec.next_rec == nil then
break
else
rec = rec.next_rec
idx = rec.data_begin
end
end
return {
host=host,
user=user,
pass=pass,
native=native
}
end
local read_records = function(filename)
local content = {}
local content_len = 0
local file = io.open(filename, 'rb')
while file ~= nil do
local buffer = file:read(1024)
if buffer == nil then
break
end
for i = 1, #buffer do
content[content_len+i] = buffer:byte(i)
end
content_len = content_len + #buffer
end
if file ~= nil then
file:close()
end
local idx = 1
while idx <= content_len do
local rec = dispatch_record(content, idx)
if 0 < rec.rec_type and rec.rec_type <= 6 then
local record = parse_record(content, rec)
print(record.host, record.user, record.pass, string.len(record.pass), record.native)
end
idx = idx + rec.block_len
end
return record
end
read_records('/usr/local/var/mysql/mysql/user.MYD')
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