<p>I am looking for a light SQLite reader, I only need it to be able to read from a database file. I would like it to be PURE Go, no cgo. All the examples i find are cgo and include a bunch of usless stuff for me.</p>
<p>I found a example in VB.net that does this;</p>
<pre><code>'**************************************************************
'
' Coded By: RockingWithTheBest
'
' v 0.1
'
'
' A Handler for SQLite without needing the sqlite3.dll!
' You can read every table and value from database, but
' there is no support for input. Also no support for
' journal files and overflow pages, maybe i will add
' that in a later release.
'
'
' Have Fun!
'
' If u want to learn more about or enhance it then visit:
' http://www.sqlite.org/fileformat.html
'
' If you copy or modify it, please add me to credits!
'
' Questions etc. to: peterrlustig@googlemail.com
'
'**************************************************************
'
' Example:
'
' Dim SQLDatabase = New SQLiteHandler("C:\Temp\Login Data")
' SQLDatabase.ReadTable("logins")
'
' MsgBox(GetValue(SQLDatabase.GetValue(0, "username_value")))
'
'**************************************************************
Imports System.IO
Public Class SQLiteHandler
Private db_bytes() As Byte
Private page_size As UInt16
Private encoding As UInt64
Private master_table_entries() As sqlite_master_entry
Private SQLDataTypeSize() As Byte = New Byte() {0, 1, 2, 3, 4, 6, 8, 8, 0, 0}
Private table_entries() As table_entry
Private field_names() As String
Private Structure record_header_field
Dim size As Int64
Dim type As Int64
End Structure
Private Structure table_entry
Dim row_id As Int64
Dim content() As String
End Structure
Private Structure sqlite_master_entry
Dim row_id As Int64
Dim item_type As String
Dim item_name As String
Dim astable_name As String
Dim root_num As Int64
Dim sql_statement As String
End Structure
'Needs BigEndian
'GetVariableLength
' returns the endindex of an variable length integer
Private Function GVL(ByVal startIndex As Integer) As Integer
Try
If startIndex > db_bytes.Length Then Return Nothing
For i = startIndex To startIndex + 8 Step 1
If i > db_bytes.Length - 1 Then
Return Nothing
ElseIf (db_bytes(i) And &H80) <> &H80 Then
Return i
End If
Next
Return startIndex + 8
Catch : End Try
End Function
' Eingaberichtung BigEndian
' ConvertVariableLength
Private Function CVL(ByVal startIndex As Integer, ByVal endIndex As Integer) As Int64
Try
endIndex = endIndex + 1
Dim retus(7) As Byte
Dim Length = endIndex - startIndex
Dim Bit64 As Boolean = False
If Length = 0 Or Length > 9 Then Return Nothing
If Length = 1 Then
retus(0) = (db_bytes(startIndex) And &H7F)
Return BitConverter.ToInt64(retus, 0)
End If
If Length = 9 Then
' Ein Byte wird nämlich grad hinzugefügt
Bit64 = True
End If
Dim j As Integer = 1
Dim k As Integer = 7
Dim y As Integer = 0
If Bit64 Then
retus(0) = db_bytes(endIndex - 1)
endIndex = endIndex - 1
y = 1
End If
For i = (endIndex - 1) To startIndex Step -1
If (i - 1) >= startIndex Then
retus(y) = ((db_bytes(i) >> (j - 1)) And (&HFF >> j)) Or (db_bytes(i - 1) << k)
j = j + 1
y = y + 1
k = k - 1
Else
If Not Bit64 Then retus(y) = ((db_bytes(i) >> (j - 1)) And (&HFF >> j))
End If
Next
Return BitConverter.ToInt64(retus, 0)
Catch : End Try
End Function
'Checks if a number is odd
Private Function IsOdd(ByVal value As Int64) As Boolean
Return (value And 1) = 1
End Function
'Big Endian Conversation
Private Function ConvertToInteger(ByVal startIndex As Integer, ByVal Size As Integer) As UInt64
Try
If Size > 8 Or Size = 0 Then Return Nothing
Dim retVal As UInt64 = 0
For i = 0 To Size - 1 Step 1
retVal = ((retVal << 8) Or db_bytes(startIndex + i))
Next
Return retVal
Catch : End Try
End Function
Private Sub ReadMasterTable(ByVal Offset As UInt64)
Try
If db_bytes(Offset) = &HD Then 'Leaf node
'Length for setting the array length for the entries
Dim Length As UInt16 = ConvertToInteger(Offset + 3, 2) - 1
Dim ol As Integer = 0
If Not master_table_entries Is Nothing Then
ol = master_table_entries.Length
ReDim Preserve master_table_entries(master_table_entries.Length + Length)
Else
ReDim master_table_entries(Length)
End If
Dim ent_offset As UInt64
For i = 0 To Length Step 1
ent_offset = ConvertToInteger(Offset + 8 + (i * 2), 2)
If Offset <> 100 Then ent_offset = ent_offset + Offset
'Table Cell auslesen
Dim t = GVL(ent_offset)
Dim size As Int64 = CVL(ent_offset, t)
Dim s = GVL(ent_offset + (t - ent_offset) + 1)
master_table_entries(ol + i).row_id = CVL(ent_offset + (t - ent_offset) + 1, s)
'Table Content
'Resetting the offset
ent_offset = ent_offset + (s - ent_offset) + 1
'Now get to the Record Header
t = GVL(ent_offset)
s = t
Dim Rec_Header_Size As Int64 = CVL(ent_offset, t) 'Record Header Length
Dim Field_Size(4) As Int64
'Now get the field sizes and fill in the Values
For j = 0 To 4 Step 1
t = s + 1
s = GVL(t)
Field_Size(j) = CVL(t, s)
If Field_Size(j) > 9 Then
If IsOdd(Field_Size(j)) Then
Field_Size(j) = (Field_Size(j) - 13) / 2
Else
Field_Size(j) = (Field_Size(j) - 12) / 2
End If
Else
Field_Size(j) = SQLDataTypeSize(Field_Size(j))
End If
Next
' Wir lesen nur unbedingt notwendige Sachen aus
If encoding = 1 Then
master_table_entries(ol + i).item_type = System.Text.Encoding.Default.GetString(db_bytes, ent_offset + Rec_Header_Size, Field_Size(0))
ElseIf encoding = 2 Then
master_table_entries(ol + i).item_type = System.Text.Encoding.Unicode.GetString(db_bytes, ent_offset + Rec_Header_Size, Field_Size(0))
ElseIf encoding = 3 Then
master_table_entries(ol + i).item_type = System.Text.Encoding.BigEndianUnicode.GetString(db_bytes, ent_offset + Rec_Header_Size, Field_Size(0))
End If
If encoding = 1 Then
master_table_entries(ol + i).item_name = System.Text.Encoding.Default.GetString(db_bytes, ent_offset + Rec_Header_Size + Field_Size(0), Field_Size(1))
ElseIf encoding = 2 Then
master_table_entries(ol + i).item_name = System.Text.Encoding.Unicode.GetString(db_bytes, ent_offset + Rec_Header_Size + Field_Size(0), Field_Size(1))
ElseIf encoding = 3 Then
master_table_entries(ol + i).item_name = System.Text.Encoding.BigEndianUnicode.GetString(db_bytes, ent_offset + Rec_Header_Size + Field_Size(0), Field_Size(1))
End If
'master_table_entries(ol + i).astable_name = System.Text.Encoding.Default.GetString(db_bytes, ent_offset + Rec_Header_Size + Field_Size(0) + Field_Size(1), Field_Size(2))
master_table_entries(ol + i).root_num = ConvertToInteger(ent_offset + Rec_Header_Size + Field_Size(0) + Field_Size(1) + Field_Size(2), Field_Size(3))
If encoding = 1 Then
master_table_entries(ol + i).sql_statement = System.Text.Encoding.Default.GetString(db_bytes, ent_offset + Rec_Header_Size + Field_Size(0) + Field_Size(1) + Field_Size(2) + Field_Size(3), Field_Size(4))
ElseIf encoding = 2 Then
master_table_entries(ol + i).sql_statement = System.Text.Encoding.Unicode.GetString(db_bytes, ent_offset + Rec_Header_Size + Field_Size(0) + Field_Size(1) + Field_Size(2) + Field_Size(3), Field_Size(4))
ElseIf encoding = 3 Then
master_table_entries(ol + i).sql_statement = System.Text.Encoding.BigEndianUnicode.GetString(db_bytes, ent_offset + Rec_Header_Size + Field_Size(0) + Field_Size(1) + Field_Size(2) + Field_Size(3), Field_Size(4))
End If
Next
ElseIf db_bytes(Offset) = &H5 Then 'internal node
Dim Length As UInt16 = ConvertToInteger(Offset + 3, 2) - 1
Dim ent_offset As UInt16
For i = 0 To Length Step 1
ent_offset = ConvertToInteger(Offset + 12 + (i * 2), 2)
If Offset = 100 Then
ReadMasterTable((ConvertToInteger(ent_offset, 4) - 1) * page_size)
Else
ReadMasterTable((ConvertToInteger(Offset + ent_offset, 4) - 1) * page_size)
End If
Next
ReadMasterTable((ConvertToInteger(Offset + 8, 4) - 1) * page_size)
End If
Catch : End Try
End Sub
Private Function ReadTableFromOffset(ByVal Offset As UInt64) As Boolean
Try
If db_bytes(Offset) = &HD Then 'Leaf node
'Length for setting the array length for the entries
Dim Length As UInt16 = ConvertToInteger(Offset + 3, 2) - 1
Dim ol As Integer = 0
If Not table_entries Is Nothing Then
ol = table_entries.Length
ReDim Preserve table_entries(table_entries.Length + Length)
Else
ReDim table_entries(Length)
End If
Dim ent_offset As UInt64
For i = 0 To Length Step 1
ent_offset = ConvertToInteger(Offset + 8 + (i * 2), 2)
If Offset <> 100 Then ent_offset = ent_offset + Offset
'Table Cell auslesen
Dim t = GVL(ent_offset)
Dim size As Int64 = CVL(ent_offset, t)
Dim s = GVL(ent_offset + (t - ent_offset) + 1)
table_entries(ol + i).row_id = CVL(ent_offset + (t - ent_offset) + 1, s)
'Table Content
'Resetting the offset
ent_offset = ent_offset + (s - ent_offset) + 1
'Now get to the Record Header
t = GVL(ent_offset)
s = t
Dim Rec_Header_Size As Int64 = CVL(ent_offset, t) 'Record Header Length
Dim Field_Size() As record_header_field
Dim size_read As Int64 = (ent_offset - t) + 1
Dim j = 0
'Now get the field sizes and fill in the Values
While size_read < Rec_Header_Size
ReDim Preserve Field_Size(j)
t = s + 1
s = GVL(t)
Field_Size(j).type = CVL(t, s)
If Field_Size(j).type > 9 Then
If IsOdd(Field_Size(j).type) Then
Field_Size(j).size = (Field_Size(j).type - 13) / 2
Else
Field_Size(j).size = (Field_Size(j).type - 12) / 2
End If
Else
Field_Size(j).size = SQLDataTypeSize(Field_Size(j).type)
End If
size_read = size_read + (s - t) + 1
j = j + 1
End While
ReDim table_entries(ol + i).content(Field_Size.Length - 1)
Dim counter As Integer = 0
For k = 0 To Field_Size.Length - 1 Step 1
If Field_Size(k).type > 9 Then
If Not IsOdd(Field_Size(k).type) Then
If encoding = 1 Then
table_entries(ol + i).content(k) = System.Text.Encoding.Default.GetString(db_bytes, ent_offset + Rec_Header_Size + counter, Field_Size(k).size)
ElseIf encoding = 2 Then
table_entries(ol + i).content(k) = System.Text.Encoding.Unicode.GetString(db_bytes, ent_offset + Rec_Header_Size + counter, Field_Size(k).size)
ElseIf encoding = 3 Then
table_entries(ol + i).content(k) = System.Text.Encoding.BigEndianUnicode.GetString(db_bytes, ent_offset + Rec_Header_Size + counter, Field_Size(k).size)
End If
Else
table_entries(ol + i).content(k) = System.Text.Encoding.Default.GetString(db_bytes, ent_offset + Rec_Header_Size + counter, Field_Size(k).size)
End If
Else
table_entries(ol + i).content(k) = CStr(ConvertToInteger(ent_offset + Rec_Header_Size + counter, Field_Size(k).size))
End If
counter = counter + Field_Size(k).size
Next
Next
ElseIf db_bytes(Offset) = &H5 Then 'internal node
Dim Length As UInt16 = ConvertToInteger(Offset + 3, 2) - 1
Dim ent_offset As UInt16
For i = 0 To Length Step 1
ent_offset = ConvertToInteger(Offset + 12 + (i * 2), 2)
ReadTableFromOffset((ConvertToInteger(Offset + ent_offset, 4) - 1) * page_size)
Next
ReadTableFromOffset((ConvertToInteger(Offset + 8, 4) - 1) * page_size)
End If
Return True
Catch : End Try
End Function
' Reads a complete table with all entries in it
Public Function ReadTable(ByVal TableName As String) As Boolean
Try
' First loop through sqlite_master and look if table exists
Dim found As Integer = -1
For i = 0 To master_table_entries.Length Step 1
If master_table_entries(i).item_name.ToLower().CompareTo(TableName.ToLower()) = 0 Then
found = i
Exit For
End If
Next
If found = -1 Then Return False
Dim fields() = master_table_entries(found).sql_statement.Substring(master_table_entries(found).sql_statement.IndexOf("(") + 1).Split(",")
For i = 0 To fields.Length - 1 Step 1
fields(i) = LTrim(fields(i))
Dim index = fields(i).IndexOf(" ")
If index > 0 Then fields(i) = fields(i).Substring(0, index)
If fields(i).IndexOf("UNIQUE") = 0 Then
Exit For
Else
ReDim Preserve field_names(i)
field_names(i) = fields(i)
End If
Next
Return ReadTableFromOffset((master_table_entries(found).root_num - 1) * page_size)
Catch : End Try
End Function
' Returns the row count of current table
Public Function GetRowCount() As Integer
Return table_entries.Length
End Function
' Returns a Value from current table in row row_num with field number field
Public Function GetValue(ByVal row_num As Integer, ByVal field As Integer) As String
Try
If row_num >= table_entries.Length Then Return Nothing
If field >= table_entries(row_num).content.Length Then Return Nothing
Return table_entries(row_num).content(field)
Catch : End Try
End Function
' Returns a Value from current table in row row_num with field name field
Public Function GetValue(ByVal row_num As Integer, ByVal field As String) As String
Try
Dim found As Integer = -1
For i = 0 To field_names.Length Step 1
If field_names(i).ToLower().CompareTo(field.ToLower()) = 0 Then
found = i
Exit For
End If
Next
If found = -1 Then Return Nothing
Return GetValue(row_num, found)
Catch : End Try
End Function
' Returns a String-Array with all Tablenames
Public Function GetTableNames() As String()
Try
Dim retVal As String()
Dim arr = 0
For i = 0 To master_table_entries.Length - 1 Step 1
If master_table_entries(i).item_type = "table" Then
ReDim Preserve retVal(arr)
retVal(arr) = master_table_entries(i).item_name
arr = arr + 1
End If
Next
Return retVal
Catch : End Try
End Function
' Constructor
Public Sub New(ByVal baseName As String)
Try
'Page Number n is page_size*(n-1)
If File.Exists(baseName) Then
FileOpen(1, baseName, OpenMode.Binary, OpenAccess.Read, OpenShare.Shared)
Dim asi As String = Space(LOF(1))
FileGet(1, asi)
FileClose(1)
db_bytes = System.Text.Encoding.Default.GetBytes(asi)
If System.Text.Encoding.Default.GetString(db_bytes, 0, 15).CompareTo("SQLite format 3") <> 0 Then
Throw New Exception("Not a valid SQLite 3 Database File")
End
End If
If db_bytes(52) <> 0 Then
Throw New Exception("Auto-vacuum capable database is not supported")
End
ElseIf ConvertToInteger(44, 4) >= 4 Then
Throw New Exception("No supported Schema layer file-format")
End
End If
page_size = ConvertToInteger(16, 2)
encoding = ConvertToInteger(56, 4)
If encoding = 0 Then encoding = 1
'Now we read the sqlite_master table
'Offset is 100 in first page
ReadMasterTable(100)
End If
Catch : End Try
End Sub
End Class
</code></pre>
<p>Though i have no idea how to convert it to Go</p>
<hr/>**评论：**<br/><br/>j_d_q: <pre><p>No useful content, here, just a thought: link to the code or create a gist. On mobile, it took me almost 19 1/2 minutes to scroll to the comments</p></pre>TheMerovius: <pre><p>Googling 8s, I found this: <a href="https://github.com/sbinet/sqlite3" rel="nofollow">https://github.com/sbinet/sqlite3</a>
Probably not maintained and somewhat likely not working, but that what it'd take; re-implementing sqlite in go. Because sqlite is an embedded database, there really are just two ways to use it: embed it (i.e. use cgo) or reimplement it.
Most people won't find the latter very rewarding, which is why I assume you'll have trouble finding it.</p></pre>
