Simple HTTP GET function
Posted: Sun Nov 04, 2007 11:45 pm
Based on an idea by Thalius, here's a simplified HTTP GET function:
And here's an example:
The function returns zero on success - negative return values indicate a technical error, as indicated by the #HTTP_ERROR-constants. Positive return values indicate a HTTP status code, e.g. the server reported an error.
The function will follow redirects.
Edit: minor fixes
Edit: local variables declared with Protected instead of Define
Code: Select all
; HTTP_GET.pbi
; by Rasmus Schultz
; Version 1.0c
; Based on a technique by Marius Eckardt (Thalius)
#HTTP_BUFFER_SIZE = 4096 ; receive buffer size
#HTTP_IDLE_DELAY = 20 ; delay during inactivity
#HTTP_LAG_DELAY = 50 ; delay during little activity
#HTTP_TIMEOUT = 10000 ; timeout in milliseconds
#HTTP_OK = 0
#HTTP_ERROR_CONNECT = -1 ; Unable to connect to the specified server
#HTTP_ERROR_MEMORY = -2 ; Unable to allocate memory for response buffer
#HTTP_ERROR_TIMEOUT = -3 ; #HTTP_TIMEOUT exceeded
#HTTP_ERROR_FILE = -4 ; Local file could not be created
#HTTP_ERROR_PROTOCOL = -5 ; Unknown HTTP protocol (version 1.0 or 1.1 required)
Enumeration ; Parser states
#HTTP_STATE_EXPECT_HEADER
#HTTP_STATE_HEADER
#HTTP_STATE_DATA
EndEnumeration
Macro HTTP_Debug(Str)
Debug Str ; comment out this line to disable debugging messages
EndMacro
Procedure HTTP_GET(URL.s, LocalFilename.s)
; function returns 0 on successful download (HTTP status 200)
; negative number in case of tehnical errors (see #HTTP_ERROR codes above)
; or positive number in case of HTTP status code other than "200"
Protected Host.s ; Server's hostname
Protected Path.s ; Remote path
Protected Port.l = 80 ; Port number
Protected Pos.l ; Used for various string operations
Protected Con.l ; Connection ID
Protected Request.s ; HTTP request headers
Protected CRLF.s = Chr(13) + Chr(10)
; Parse URL:
If FindString(URL, "http://", 1) = 1 : URL = Right(URL, Len(URL)-7) : EndIf
Pos = FindString(URL, "/", 1)
If Pos = 0
Host = URL
Path = "/"
Else
Host = Left(URL, Pos-1)
Path = Right(URL, Len(URL)-Pos+1)
EndIf
Pos = FindString(Host, ":", 1)
If Pos > 0
Port = Val(Right(Host, Len(Host)-Pos))
Host = Left(Host, Pos-1)
EndIf
HTTP_Debug("Host: " + Chr(34) + Host + Chr(34))
HTTP_Debug("Path: " + Chr(34) + Path + Chr(34))
HTTP_Debug("Port: " + Str(Port))
; Allocate response buffer:
Protected *Buffer
*Buffer = AllocateMemory(#HTTP_BUFFER_SIZE)
If Not *Buffer : ProcedureReturn #HTTP_ERROR_MEMORY : EndIf
; Open connection:
Con = OpenNetworkConnection(Host, Port)
If Con = 0 : ProcedureReturn #HTTP_ERROR_CONNECT : EndIf
; Send HTTP request:
Request = "GET " + Path + " HTTP/1.0" + CRLF
Request + "Host: " + Host + CRLF
Request + "Connection: Close" + CRLF + CRLF
SendNetworkString(Con, Request)
; Create output file:
Protected FileID.l = 0
; Process response:
Protected Exit.l = #False ; Exit flag
Protected Bytes.l ; Number of bytes received
Protected Time.l = ElapsedMilliseconds() ; Time of last data reception
Protected Status.l = #HTTP_OK ; Status flag
Protected State.l = #HTTP_STATE_EXPECT_HEADER
Protected String.s ; Parser input
Protected Index.l ; Parser position
Protected Char.s ; Parser char
Protected Header.s ; Current header
Protected HTTP_Protocol.s ; HTTP protocol version
Protected HTTP_Status.l = 0 ; HTTP status code
Protected Redirected.b = #False
Repeat
If NetworkClientEvent(Con) = #PB_NetworkEvent_Data
Repeat
Bytes = ReceiveNetworkData(Con, *Buffer, #HTTP_BUFFER_SIZE)
If Bytes = 0
Exit = #True
Else
If Bytes < #HTTP_BUFFER_SIZE : Delay(#HTTP_LAG_DELAY) : EndIf
HTTP_Debug("Received: " + Str(Bytes) + " bytes")
If State = #HTTP_STATE_DATA
WriteData(FileID, *Buffer, Bytes)
Else
String = PeekS(*Buffer, Bytes, #PB_Ascii)
Index = 0
Repeat
Index + 1
Char = Mid(String, Index, 1)
Select State
Case #HTTP_STATE_EXPECT_HEADER
If Char = Chr(10)
State = #HTTP_STATE_DATA
HTTP_Debug("Creating file: " + LocalFilename)
FileID = CreateFile(#PB_Any, LocalFilename)
If FileID = 0
Exit = #True
Status = #HTTP_ERROR_FILE
ElseIf Index < Bytes
WriteData(FileID, *Buffer+Index, Bytes-Index)
EndIf
ElseIf Char = Chr(13)
; (ignore)
Else
Header = Char
State = #HTTP_STATE_HEADER
EndIf
Case #HTTP_STATE_HEADER
If Char = Chr(10)
If HTTP_Status = 0
HTTP_Protocol = StringField(StringField(Header, 1, " "), 2, "/")
HTTP_Status = Val(StringField(Header, 2, " "))
If ((HTTP_Protocol <> "1.0") And (HTTP_Protocol <> "1.1")) Or (StringField(StringField(Header, 1, " "), 1, "/") <> "HTTP") Or (HTTP_Status = 0)
HTTP_Debug("HTTP Protocol error!")
Exit = #True
Status = #HTTP_ERROR_PROTOCOL
EndIf
HTTP_Debug("HTTP Protocol " + HTTP_Protocol + ", Status " + Str(HTTP_Status))
If (HTTP_Status >= 300) And (HTTP_Status < 400)
HTTP_Debug("Redirection...")
Redirected = #True
ElseIf HTTP_Status <> 200
Status = HTTP_Status
Exit = #True
HTTP_Debug("Status <> 200 - abort!")
EndIf
ElseIf Left(Header, 10) = "Location: "
Status = HTTP_GET(Right(Header, Len(Header)-10), LocalFilename)
Exit = #True
Else
HTTP_Debug(Header)
EndIf
State = #HTTP_STATE_EXPECT_HEADER
ElseIf Char = Chr(13)
; (ignore)
Else
Header + Char
EndIf
EndSelect
Until (State = #HTTP_STATE_DATA) Or (Index = Bytes) Or (Exit = #True)
EndIf
Time = ElapsedMilliseconds()
EndIf
Until Exit = #True
Else
HTTP_Debug("Idle...")
Delay(#HTTP_IDLE_DELAY)
If ElapsedMilliseconds() - Time > #HTTP_TIMEOUT
Exit = #True
Status = #HTTP_ERROR_TIMEOUT
EndIf
EndIf
Until Exit = #True
; Close and finish:
CloseNetworkConnection(Con)
FreeMemory(*Buffer)
If FileID <> 0 : CloseFile(FileID) : EndIf
ProcedureReturn Status
EndProcedure
Code: Select all
; --- Example:
If InitNetwork() = 0
Debug "No TCP provider..."
Else
Status.l = HTTP_GET("http://www.wavemage.com/edscore/5-EndTitle.mp3", GetCurrentDirectory()+"test.mp3")
Debug "DownloadFile returned: " + Str(Status)
EndIf
The function will follow redirects.
Edit: minor fixes
Edit: local variables declared with Protected instead of Define
