p2p: add network simulation framework (#14982)

This commit introduces a network simulation framework which
can be used to run simulated networks of devp2p nodes. The
intention is to use this for testing protocols, performing
benchmarks and visualising emergent network behaviour.

1 files changed, 656 insertions, 0 deletions

diff --git a/vendor/github.com/julienschmidt/httprouter/tree.go b/vendor/github.com/julienschmidt/httprouter/tree.go
new file mode 100644
index 000000000..a8fa98b04
--- /dev/null
+++ b/vendor/github.com/julienschmidt/httprouter/tree.go
@@ -0,0 +1,656 @@
+// Copyright 2013 Julien Schmidt. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be found
+// in the LICENSE file.
+
+package httprouter
+
+import (
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+func min(a, b int) int {
+	if a <= b {
+		return a
+	}
+	return b
+}
+
+func countParams(path string) uint8 {
+	var n uint
+	for i := 0; i < len(path); i++ {
+		if path[i] != ':' && path[i] != '*' {
+			continue
+		}
+		n++
+	}
+	if n >= 255 {
+		return 255
+	}
+	return uint8(n)
+}
+
+type nodeType uint8
+
+const (
+	static nodeType = iota // default
+	root
+	param
+	catchAll
+)
+
+type node struct {
+	path      string
+	wildChild bool
+	nType     nodeType
+	maxParams uint8
+	indices   string
+	children  []*node
+	handle    Handle
+	priority  uint32
+}
+
+// increments priority of the given child and reorders if necessary
+func (n *node) incrementChildPrio(pos int) int {
+	n.children[pos].priority++
+	prio := n.children[pos].priority
+
+	// adjust position (move to front)
+	newPos := pos
+	for newPos > 0 && n.children[newPos-1].priority < prio {
+		// swap node positions
+		n.children[newPos-1], n.children[newPos] = n.children[newPos], n.children[newPos-1]
+
+		newPos--
+	}
+
+	// build new index char string
+	if newPos != pos {
+		n.indices = n.indices[:newPos] + // unchanged prefix, might be empty
+			n.indices[pos:pos+1] + // the index char we move
+			n.indices[newPos:pos] + n.indices[pos+1:] // rest without char at 'pos'
+	}
+
+	return newPos
+}
+
+// addRoute adds a node with the given handle to the path.
+// Not concurrency-safe!
+func (n *node) addRoute(path string, handle Handle) {
+	fullPath := path
+	n.priority++
+	numParams := countParams(path)
+
+	// non-empty tree
+	if len(n.path) > 0 || len(n.children) > 0 {
+	walk:
+		for {
+			// Update maxParams of the current node
+			if numParams > n.maxParams {
+				n.maxParams = numParams
+			}
+
+			// Find the longest common prefix.
+			// This also implies that the common prefix contains no ':' or '*'
+			// since the existing key can't contain those chars.
+			i := 0
+			max := min(len(path), len(n.path))
+			for i < max && path[i] == n.path[i] {
+				i++
+			}
+
+			// Split edge
+			if i < len(n.path) {
+				child := node{
+					path:      n.path[i:],
+					wildChild: n.wildChild,
+					nType:     static,
+					indices:   n.indices,
+					children:  n.children,
+					handle:    n.handle,
+					priority:  n.priority - 1,
+				}
+
+				// Update maxParams (max of all children)
+				for i := range child.children {
+					if child.children[i].maxParams > child.maxParams {
+						child.maxParams = child.children[i].maxParams
+					}
+				}
+
+				n.children = []*node{&child}
+				// []byte for proper unicode char conversion, see #65
+				n.indices = string([]byte{n.path[i]})
+				n.path = path[:i]
+				n.handle = nil
+				n.wildChild = false
+			}
+
+			// Make new node a child of this node
+			if i < len(path) {
+				path = path[i:]
+
+				if n.wildChild {
+					n = n.children[0]
+					n.priority++
+
+					// Update maxParams of the child node
+					if numParams > n.maxParams {
+						n.maxParams = numParams
+					}
+					numParams--
+
+					// Check if the wildcard matches
+					if len(path) >= len(n.path) && n.path == path[:len(n.path)] &&
+						// Check for longer wildcard, e.g. :name and :names
+						(len(n.path) >= len(path) || path[len(n.path)] == '/') {
+						continue walk
+					} else {
+						// Wildcard conflict
+						var pathSeg string
+						if n.nType == catchAll {
+							pathSeg = path
+						} else {
+							pathSeg = strings.SplitN(path, "/", 2)[0]
+						}
+						prefix := fullPath[:strings.Index(fullPath, pathSeg)] + n.path
+						panic("'" + pathSeg +
+							"' in new path '" + fullPath +
+							"' conflicts with existing wildcard '" + n.path +
+							"' in existing prefix '" + prefix +
+							"'")
+					}
+				}
+
+				c := path[0]
+
+				// slash after param
+				if n.nType == param && c == '/' && len(n.children) == 1 {
+					n = n.children[0]
+					n.priority++
+					continue walk
+				}
+
+				// Check if a child with the next path byte exists
+				for i := 0; i < len(n.indices); i++ {
+					if c == n.indices[i] {
+						i = n.incrementChildPrio(i)
+						n = n.children[i]
+						continue walk
+					}
+				}
+
+				// Otherwise insert it
+				if c != ':' && c != '*' {
+					// []byte for proper unicode char conversion, see #65
+					n.indices += string([]byte{c})
+					child := &node{
+						maxParams: numParams,
+					}
+					n.children = append(n.children, child)
+					n.incrementChildPrio(len(n.indices) - 1)
+					n = child
+				}
+				n.insertChild(numParams, path, fullPath, handle)
+				return
+
+			} else if i == len(path) { // Make node a (in-path) leaf
+				if n.handle != nil {
+					panic("a handle is already registered for path '" + fullPath + "'")
+				}
+				n.handle = handle
+			}
+			return
+		}
+	} else { // Empty tree
+		n.insertChild(numParams, path, fullPath, handle)
+		n.nType = root
+	}
+}
+
+func (n *node) insertChild(numParams uint8, path, fullPath string, handle Handle) {
+	var offset int // already handled bytes of the path
+
+	// find prefix until first wildcard (beginning with ':'' or '*'')
+	for i, max := 0, len(path); numParams > 0; i++ {
+		c := path[i]
+		if c != ':' && c != '*' {
+			continue
+		}
+
+		// find wildcard end (either '/' or path end)
+		end := i + 1
+		for end < max && path[end] != '/' {
+			switch path[end] {
+			// the wildcard name must not contain ':' and '*'
+			case ':', '*':
+				panic("only one wildcard per path segment is allowed, has: '" +
+					path[i:] + "' in path '" + fullPath + "'")
+			default:
+				end++
+			}
+		}
+
+		// check if this Node existing children which would be
+		// unreachable if we insert the wildcard here
+		if len(n.children) > 0 {
+			panic("wildcard route '" + path[i:end] +
+				"' conflicts with existing children in path '" + fullPath + "'")
+		}
+
+		// check if the wildcard has a name
+		if end-i < 2 {
+			panic("wildcards must be named with a non-empty name in path '" + fullPath + "'")
+		}
+
+		if c == ':' { // param
+			// split path at the beginning of the wildcard
+			if i > 0 {
+				n.path = path[offset:i]
+				offset = i
+			}
+
+			child := &node{
+				nType:     param,
+				maxParams: numParams,
+			}
+			n.children = []*node{child}
+			n.wildChild = true
+			n = child
+			n.priority++
+			numParams--
+
+			// if the path doesn't end with the wildcard, then there
+			// will be another non-wildcard subpath starting with '/'
+			if end < max {
+				n.path = path[offset:end]
+				offset = end
+
+				child := &node{
+					maxParams: numParams,
+					priority:  1,
+				}
+				n.children = []*node{child}
+				n = child
+			}
+
+		} else { // catchAll
+			if end != max || numParams > 1 {
+				panic("catch-all routes are only allowed at the end of the path in path '" + fullPath + "'")
+			}
+
+			if len(n.path) > 0 && n.path[len(n.path)-1] == '/' {
+				panic("catch-all conflicts with existing handle for the path segment root in path '" + fullPath + "'")
+			}
+
+			// currently fixed width 1 for '/'
+			i--
+			if path[i] != '/' {
+				panic("no / before catch-all in path '" + fullPath + "'")
+			}
+
+			n.path = path[offset:i]
+
+			// first node: catchAll node with empty path
+			child := &node{
+				wildChild: true,
+				nType:     catchAll,
+				maxParams: 1,
+			}
+			n.children = []*node{child}
+			n.indices = string(path[i])
+			n = child
+			n.priority++
+
+			// second node: node holding the variable
+			child = &node{
+				path:      path[i:],
+				nType:     catchAll,
+				maxParams: 1,
+				handle:    handle,
+				priority:  1,
+			}
+			n.children = []*node{child}
+
+			return
+		}
+	}
+
+	// insert remaining path part and handle to the leaf
+	n.path = path[offset:]
+	n.handle = handle
+}
+
+// Returns the handle registered with the given path (key). The values of
+// wildcards are saved to a map.
+// If no handle can be found, a TSR (trailing slash redirect) recommendation is
+// made if a handle exists with an extra (without the) trailing slash for the
+// given path.
+func (n *node) getValue(path string) (handle Handle, p Params, tsr bool) {
+walk: // outer loop for walking the tree
+	for {
+		if len(path) > len(n.path) {
+			if path[:len(n.path)] == n.path {
+				path = path[len(n.path):]
+				// If this node does not have a wildcard (param or catchAll)
+				// child,  we can just look up the next child node and continue
+				// to walk down the tree
+				if !n.wildChild {
+					c := path[0]
+					for i := 0; i < len(n.indices); i++ {
+						if c == n.indices[i] {
+							n = n.children[i]
+							continue walk
+						}
+					}
+
+					// Nothing found.
+					// We can recommend to redirect to the same URL without a
+					// trailing slash if a leaf exists for that path.
+					tsr = (path == "/" && n.handle != nil)
+					return
+
+				}
+
+				// handle wildcard child
+				n = n.children[0]
+				switch n.nType {
+				case param:
+					// find param end (either '/' or path end)
+					end := 0
+					for end < len(path) && path[end] != '/' {
+						end++
+					}
+
+					// save param value
+					if p == nil {
+						// lazy allocation
+						p = make(Params, 0, n.maxParams)
+					}
+					i := len(p)
+					p = p[:i+1] // expand slice within preallocated capacity
+					p[i].Key = n.path[1:]
+					p[i].Value = path[:end]
+
+					// we need to go deeper!
+					if end < len(path) {
+						if len(n.children) > 0 {
+							path = path[end:]
+							n = n.children[0]
+							continue walk
+						}
+
+						// ... but we can't
+						tsr = (len(path) == end+1)
+						return
+					}
+
+					if handle = n.handle; handle != nil {
+						return
+					} else if len(n.children) == 1 {
+						// No handle found. Check if a handle for this path + a
+						// trailing slash exists for TSR recommendation
+						n = n.children[0]
+						tsr = (n.path == "/" && n.handle != nil)
+					}
+
+					return
+
+				case catchAll:
+					// save param value
+					if p == nil {
+						// lazy allocation
+						p = make(Params, 0, n.maxParams)
+					}
+					i := len(p)
+					p = p[:i+1] // expand slice within preallocated capacity
+					p[i].Key = n.path[2:]
+					p[i].Value = path
+
+					handle = n.handle
+					return
+
+				default:
+					panic("invalid node type")
+				}
+			}
+		} else if path == n.path {
+			// We should have reached the node containing the handle.
+			// Check if this node has a handle registered.
+			if handle = n.handle; handle != nil {
+				return
+			}
+
+			if path == "/" && n.wildChild && n.nType != root {
+				tsr = true
+				return
+			}
+
+			// No handle found. Check if a handle for this path + a
+			// trailing slash exists for trailing slash recommendation
+			for i := 0; i < len(n.indices); i++ {
+				if n.indices[i] == '/' {
+					n = n.children[i]
+					tsr = (len(n.path) == 1 && n.handle != nil) ||
+						(n.nType == catchAll && n.children[0].handle != nil)
+					return
+				}
+			}
+
+			return
+		}
+
+		// Nothing found. We can recommend to redirect to the same URL with an
+		// extra trailing slash if a leaf exists for that path
+		tsr = (path == "/") ||
+			(len(n.path) == len(path)+1 && n.path[len(path)] == '/' &&
+				path == n.path[:len(n.path)-1] && n.handle != nil)
+		return
+	}
+}
+
+// Makes a case-insensitive lookup of the given path and tries to find a handler.
+// It can optionally also fix trailing slashes.
+// It returns the case-corrected path and a bool indicating whether the lookup
+// was successful.
+func (n *node) findCaseInsensitivePath(path string, fixTrailingSlash bool) (ciPath []byte, found bool) {
+	return n.findCaseInsensitivePathRec(
+		path,
+		strings.ToLower(path),
+		make([]byte, 0, len(path)+1), // preallocate enough memory for new path
+		[4]byte{},                    // empty rune buffer
+		fixTrailingSlash,
+	)
+}
+
+// shift bytes in array by n bytes left
+func shiftNRuneBytes(rb [4]byte, n int) [4]byte {
+	switch n {
+	case 0:
+		return rb
+	case 1:
+		return [4]byte{rb[1], rb[2], rb[3], 0}
+	case 2:
+		return [4]byte{rb[2], rb[3]}
+	case 3:
+		return [4]byte{rb[3]}
+	default:
+		return [4]byte{}
+	}
+}
+
+// recursive case-insensitive lookup function used by n.findCaseInsensitivePath
+func (n *node) findCaseInsensitivePathRec(path, loPath string, ciPath []byte, rb [4]byte, fixTrailingSlash bool) ([]byte, bool) {
+	loNPath := strings.ToLower(n.path)
+
+walk: // outer loop for walking the tree
+	for len(loPath) >= len(loNPath) && (len(loNPath) == 0 || loPath[1:len(loNPath)] == loNPath[1:]) {
+		// add common path to result
+		ciPath = append(ciPath, n.path...)
+
+		if path = path[len(n.path):]; len(path) > 0 {
+			loOld := loPath
+			loPath = loPath[len(loNPath):]
+
+			// If this node does not have a wildcard (param or catchAll) child,
+			// we can just look up the next child node and continue to walk down
+			// the tree
+			if !n.wildChild {
+				// skip rune bytes already processed
+				rb = shiftNRuneBytes(rb, len(loNPath))
+
+				if rb[0] != 0 {
+					// old rune not finished
+					for i := 0; i < len(n.indices); i++ {
+						if n.indices[i] == rb[0] {
+							// continue with child node
+							n = n.children[i]
+							loNPath = strings.ToLower(n.path)
+							continue walk
+						}
+					}
+				} else {
+					// process a new rune
+					var rv rune
+
+					// find rune start
+					// runes are up to 4 byte long,
+					// -4 would definitely be another rune
+					var off int
+					for max := min(len(loNPath), 3); off < max; off++ {
+						if i := len(loNPath) - off; utf8.RuneStart(loOld[i]) {
+							// read rune from cached lowercase path
+							rv, _ = utf8.DecodeRuneInString(loOld[i:])
+							break
+						}
+					}
+
+					// calculate lowercase bytes of current rune
+					utf8.EncodeRune(rb[:], rv)
+					// skipp already processed bytes
+					rb = shiftNRuneBytes(rb, off)
+
+					for i := 0; i < len(n.indices); i++ {
+						// lowercase matches
+						if n.indices[i] == rb[0] {
+							// must use a recursive approach since both the
+							// uppercase byte and the lowercase byte might exist
+							// as an index
+							if out, found := n.children[i].findCaseInsensitivePathRec(
+								path, loPath, ciPath, rb, fixTrailingSlash,
+							); found {
+								return out, true
+							}
+							break
+						}
+					}
+
+					// same for uppercase rune, if it differs
+					if up := unicode.ToUpper(rv); up != rv {
+						utf8.EncodeRune(rb[:], up)
+						rb = shiftNRuneBytes(rb, off)
+
+						for i := 0; i < len(n.indices); i++ {
+							// uppercase matches
+							if n.indices[i] == rb[0] {
+								// continue with child node
+								n = n.children[i]
+								loNPath = strings.ToLower(n.path)
+								continue walk
+							}
+						}
+					}
+				}
+
+				// Nothing found. We can recommend to redirect to the same URL
+				// without a trailing slash if a leaf exists for that path
+				return ciPath, (fixTrailingSlash && path == "/" && n.handle != nil)
+			}
+
+			n = n.children[0]
+			switch n.nType {
+			case param:
+				// find param end (either '/' or path end)
+				k := 0
+				for k < len(path) && path[k] != '/' {
+					k++
+				}
+
+				// add param value to case insensitive path
+				ciPath = append(ciPath, path[:k]...)
+
+				// we need to go deeper!
+				if k < len(path) {
+					if len(n.children) > 0 {
+						// continue with child node
+						n = n.children[0]
+						loNPath = strings.ToLower(n.path)
+						loPath = loPath[k:]
+						path = path[k:]
+						continue
+					}
+
+					// ... but we can't
+					if fixTrailingSlash && len(path) == k+1 {
+						return ciPath, true
+					}
+					return ciPath, false
+				}
+
+				if n.handle != nil {
+					return ciPath, true
+				} else if fixTrailingSlash && len(n.children) == 1 {
+					// No handle found. Check if a handle for this path + a
+					// trailing slash exists
+					n = n.children[0]
+					if n.path == "/" && n.handle != nil {
+						return append(ciPath, '/'), true
+					}
+				}
+				return ciPath, false
+
+			case catchAll:
+				return append(ciPath, path...), true
+
+			default:
+				panic("invalid node type")
+			}
+		} else {
+			// We should have reached the node containing the handle.
+			// Check if this node has a handle registered.
+			if n.handle != nil {
+				return ciPath, true
+			}
+
+			// No handle found.
+			// Try to fix the path by adding a trailing slash
+			if fixTrailingSlash {
+				for i := 0; i < len(n.indices); i++ {
+					if n.indices[i] == '/' {
+						n = n.children[i]
+						if (len(n.path) == 1 && n.handle != nil) ||
+							(n.nType == catchAll && n.children[0].handle != nil) {
+							return append(ciPath, '/'), true
+						}
+						return ciPath, false
+					}
+				}
+			}
+			return ciPath, false
+		}
+	}
+
+	// Nothing found.
+	// Try to fix the path by adding / removing a trailing slash
+	if fixTrailingSlash {
+		if path == "/" {
+			return ciPath, true
+		}
+		if len(loPath)+1 == len(loNPath) && loNPath[len(loPath)] == '/' &&
+			loPath[1:] == loNPath[1:len(loPath)] && n.handle != nil {
+			return append(ciPath, n.path...), true
+		}
+	}
+	return ciPath, false
+}